Import ciborium-ll crate. am: 9f5d17f18d am: 0da8884a60

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/ciborium-ll/+/1966261

Change-Id: I5264a4294751d351e962fcc36e717a0733d3c9c7

13 files changed, 1467 insertions, 0 deletions

diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..3de4baa
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,18 @@
+// This file is generated by cargo2android.py --run --device --dependencies.
+// Do not modify this file as changes will be overridden on upgrade.
+
+
+
+rust_library {
+    name: "libciborium_ll",
+    host_supported: true,
+    crate_name: "ciborium_ll",
+    cargo_env_compat: true,
+    cargo_pkg_version: "0.2.0",
+    srcs: ["src/lib.rs"],
+    edition: "2021",
+    rustlibs: [
+        "libciborium_io",
+        "libhalf",
+    ],
+}
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..f70a861
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,46 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2021"
+name = "ciborium-ll"
+version = "0.2.0"
+authors = ["Nathaniel McCallum <npmccallum@profian.com>"]
+description = "Low-level CBOR codec primitives"
+homepage = "https://github.com/enarx/ciborium"
+readme = "README.md"
+keywords = ["cbor"]
+categories = ["data-structures", "embedded", "encoding", "no-std", "parsing"]
+license = "Apache-2.0"
+repository = "https://github.com/enarx/ciborium"
+[dependencies.ciborium-io]
+version = "0.2.0"
+
+[dependencies.half]
+version = "1.6"
+[dev-dependencies.hex]
+version = "0.4"
+
+[features]
+alloc = []
+std = ["alloc"]
+[badges.github]
+repository = "enarx/ciborium"
+workflow = "test"
+
+[badges.is-it-maintained-issue-resolution]
+repository = "enarx/ciborium"
+
+[badges.is-it-maintained-open-issues]
+repository = "enarx/ciborium"
+
+[badges.maintenance]
+status = "actively-developed"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..97dc646
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,31 @@
+[package]
+name = "ciborium-ll"
+version = "0.2.0"
+authors = ["Nathaniel McCallum <npmccallum@profian.com>"]
+license = "Apache-2.0"
+edition = "2021"
+homepage = "https://github.com/enarx/ciborium"
+repository = "https://github.com/enarx/ciborium"
+description = "Low-level CBOR codec primitives"
+readme = "README.md"
+keywords = ["cbor"]
+categories = ["data-structures", "embedded", "encoding", "no-std", "parsing"]
+
+[badges]
+# See https://doc.rust-lang.org/cargo/reference/manifest.html#the-badges-section
+github = { repository = "enarx/ciborium", workflow = "test" }
+#github = { repository = "enarx/ciborium", workflow = "lint" }
+maintenance = { status = "actively-developed" }
+is-it-maintained-issue-resolution = { repository = "enarx/ciborium" }
+is-it-maintained-open-issues = { repository = "enarx/ciborium" }
+
+[dependencies]
+ciborium-io = { path = "../ciborium-io", version = "0.2.0" }
+half = "1.6"
+
+[dev-dependencies]
+hex = "0.4"
+
+[features]
+alloc = []
+std = ["alloc"]
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..043445b
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,53 @@
+Apache License
+Version 2.0, January 2004
+http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+"License" shall mean the terms and conditions for use, reproduction, and distribution as defined by Sections 1 through 9 of this document.
+
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+
+"You" (or "Your") shall mean an individual or Legal Entity exercising permissions granted by this License.
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+You must cause any modified files to carry prominent notices stating that You changed the files; and
+You must retain, in the Source form of any Derivative Works that You distribute, all copyright, patent, trademark, and attribution notices from the Source form of the Work, excluding those notices that do not pertain to any part of the Derivative Works; and
+If the Work includes a "NOTICE" text file as part of its distribution, then any Derivative Works that You distribute must include a readable copy of the attribution notices contained within such NOTICE file, excluding those notices that do not pertain to any part of the Derivative Works, in at least one of the following places: within a NOTICE text file distributed as part of the Derivative Works; within the Source form or documentation, if provided along with the Derivative Works; or, within a display generated by the Derivative Works, if and wherever such third-party notices normally appear. The contents of the NOTICE file are for informational purposes only and do not modify the License. You may add Your own attribution notices within Derivative Works that You distribute, alongside or as an addendum to the NOTICE text from the Work, provided that such additional attribution notices cannot be construed as modifying the License.
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+You may add Your own copyright statement to Your modifications and may provide additional or different license terms and conditions for use, reproduction, or distribution of Your modifications, or for any such Derivative Works as a whole, provided Your use, reproduction, and distribution of the Work otherwise complies with the conditions stated in this License.
+5. Submission of Contributions. Unless You explicitly state otherwise, any Contribution intentionally submitted for inclusion in the Work by You to the Licensor shall be under the terms and conditions of this License, without any additional terms or conditions. Notwithstanding the above, nothing herein shall supersede or modify the terms of any separate license agreement you may have executed with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade names, trademarks, service marks, or product names of the Licensor, except as required for reasonable and customary use in describing the origin of the Work and reproducing the content of the NOTICE file.
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+7. Disclaimer of Warranty. Unless required by applicable law or agreed to in writing, Licensor provides the Work (and each Contributor provides its Contributions) on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. You are solely responsible for determining the appropriateness of using or redistributing the Work and assume any risks associated with Your exercise of permissions under this License.
+
+8. Limitation of Liability. In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall any Contributor be liable to You for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising as a result of this License or out of the use or inability to use the Work (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if such Contributor has been advised of the possibility of such damages.
+
+9. Accepting Warranty or Additional Liability. While redistributing the Work or Derivative Works thereof, You may choose to offer, and charge a fee for, acceptance of support, warranty, indemnity, or other liability obligations and/or rights consistent with this License. However, in accepting such obligations, You may act only on Your own behalf and on Your sole responsibility, not on behalf of any other Contributor, and only if You agree to indemnify, defend, and hold each Contributor harmless for any liability incurred by, or claims asserted against, such Contributor by reason of your accepting any such warranty or additional liability.
+
+END OF TERMS AND CONDITIONS
+
+
diff --git a/METADATA b/METADATA
new file mode 100644
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--- /dev/null
+++ b/METADATA
@@ -0,0 +1,18 @@
+name: "ciborium-ll"
+description:
+    "Low-level CBOR codec primitives"
+
+third_party {
+  url {
+    type: HOMEPAGE
+    value: "https://crates.io/crates/ciborium-ll/0.2.0"
+  }
+  url {
+    type: ARCHIVE
+    value: "https://static.crates.io/crates/ciborium-ll/ciborium-ll-0.2.0.crate"
+  }
+  version: "0.2.0"
+  last_upgrade_date { year: 2022 month: 1 day: 17 }
+  license_type: NOTICE
+}
+
diff --git a/MODULE_LICENSE_APACHE2 b/MODULE_LICENSE_APACHE2
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_APACHE2
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..0faafa5
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,6 @@
+include platform/prebuilts/rust:master:/OWNERS
+# Android Hardware Security
+asbel@google.com
+jbires@google.com
+paulcrowley@google.com
+
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..2ca6306
--- /dev/null
+++ b/README.md
@@ -0,0 +1,131 @@
+[![Workflow Status](https://github.com/enarx/ciborium/workflows/test/badge.svg)](https://github.com/enarx/ciborium/actions?query=workflow%3A%22test%22)
+[![Average time to resolve an issue](https://isitmaintained.com/badge/resolution/enarx/ciborium.svg)](https://isitmaintained.com/project/enarx/ciborium "Average time to resolve an issue")
+[![Percentage of issues still open](https://isitmaintained.com/badge/open/enarx/ciborium.svg)](https://isitmaintained.com/project/enarx/ciborium "Percentage of issues still open")
+![Maintenance](https://img.shields.io/badge/maintenance-activly--developed-brightgreen.svg)
+
+# ciborium-ll
+
+Low level CBOR parsing tools
+
+This crate contains low-level types for encoding and decoding items in
+CBOR. This crate is usable in both `no_std` and `no_alloc` environments.
+To understand how this crate works, first we will look at the structure
+of a CBOR item on the wire.
+
+## Anatomy of a CBOR Item
+
+This is a brief anatomy of a CBOR item on the wire.
+
+```
++------------+-----------+
+|            |           |
+|   Major    |   Minor   |
+|  (3bits)   |  (5bits)  |
+|            |           |
++------------+-----------+
+^                        ^
+|                        |
++-----+            +-----+
+      |            |
+      |            |
+      +----------------------------+--------------+
+      |            |               |              |
+      |   Prefix   |     Affix     |    Suffix    |
+      |  (1 byte)  |  (0-8 bytes)  |  (0+ bytes)  |
+      |            |               |              |
+      +------------+---------------+--------------+
+
+      |                            |              |
+      +------------+---------------+--------------+
+                   |                       |
+                   v                       v
+
+                 Header                   Body
+```
+
+The `ciborium` crate works by providing the `Decoder` and `Encoder` types
+which provide input and output for a CBOR header (see: `Header`). From
+there, you can either handle the body yourself or use the provided utility
+functions.
+
+For more information on the CBOR format, see
+[RFC 7049](https://tools.ietf.org/html/rfc7049).
+
+## Decoding
+
+In order to decode CBOR, you will create a `Decoder` from a reader. The
+decoder instance will allow you to `Decoder::pull()` `Header` instances
+from the input.
+
+Most CBOR items are fully contained in their headers and therefore have no
+body. These items can be evaluated directly from the `Header` instance.
+
+Bytes and text items have a body but do not contain child items. Since
+both bytes and text values may be segmented, parsing them can be a bit
+tricky. Therefore, we provide helper functions to parse these types. See
+`Decoder::bytes()` and `Decoder::text()` for more details.
+
+Array and map items have a body which contains child items. These can be
+parsed by simply doing `Decoder::pull()` to parse the child items.
+
+### Example
+
+```rust
+use ciborium_ll::{Decoder, Header};
+use ciborium_io::Read as _;
+
+let input = b"\x6dHello, World!";
+let mut decoder = Decoder::from(&input[..]);
+let mut chunks = 0;
+
+match decoder.pull().unwrap() {
+    Header::Text(len) => {
+        let mut segments = decoder.text(len);
+        while let Some(mut segment) = segments.pull().unwrap() {
+            let mut buffer = [0u8; 7];
+            while let Some(chunk) = segment.pull(&mut buffer[..]).unwrap() {
+                 match chunk {
+                     "Hello, " if chunks == 0 => chunks = 1,
+                     "World!" if chunks == 1 => chunks = 2,
+                     _ => panic!("received unexpected chunk"),
+                 }
+            }
+        }
+    }
+
+    _ => panic!("received unexpected value"),
+}
+
+assert_eq!(chunks, 2);
+```
+
+## Encoding
+
+To encode values to CBOR, create an `Encoder` from a writer. The encoder
+instance provides the `Encoder::push()` method to write a `Header` value
+to the wire. CBOR item bodies can be written directly.
+
+For bytes and text, there are the `Encoder::bytes()` and `Encoder::text()`
+utility functions, respectively, which will properly segment the output
+on the wire for you.
+
+### Example
+
+```rust
+use ciborium_ll::{Encoder, Header};
+use ciborium_io::Write as _;
+
+let mut buffer = [0u8; 19];
+let mut encoder = Encoder::from(&mut buffer[..]);
+
+// Write the structure
+encoder.push(Header::Map(Some(1))).unwrap();
+encoder.push(Header::Positive(7)).unwrap();
+encoder.text("Hello, World!", 7).unwrap();
+
+// Validate our output
+encoder.flush().unwrap();
+assert_eq!(b"\xa1\x07\x7f\x67Hello, \x66World!\xff", &buffer[..]);
+```
+
+License: Apache-2.0
diff --git a/src/dec.rs b/src/dec.rs
new file mode 100644
index 0000000..8329634
--- /dev/null
+++ b/src/dec.rs
@@ -0,0 +1,174 @@
+use super::*;
+
+use ciborium_io::Read;
+
+/// An error that occurred while decoding
+#[derive(Debug)]
+pub enum Error<T> {
+    /// An error occurred while reading bytes
+    ///
+    /// Contains the underlying error reaturned while reading.
+    Io(T),
+
+    /// An error occurred while parsing bytes
+    ///
+    /// Contains the offset into the stream where the syntax error occurred.
+    Syntax(usize),
+}
+
+impl<T> From<T> for Error<T> {
+    #[inline]
+    fn from(value: T) -> Self {
+        Self::Io(value)
+    }
+}
+
+/// A decoder for deserializing CBOR items
+///
+/// This decoder manages the low-level decoding of CBOR items into `Header`
+/// objects. It also contains utility functions for parsing segmented bytes
+/// and text inputs.
+pub struct Decoder<R: Read> {
+    reader: R,
+    offset: usize,
+    buffer: Option<Title>,
+}
+
+impl<R: Read> From<R> for Decoder<R> {
+    #[inline]
+    fn from(value: R) -> Self {
+        Self {
+            reader: value,
+            offset: 0,
+            buffer: None,
+        }
+    }
+}
+
+impl<R: Read> Read for Decoder<R> {
+    type Error = R::Error;
+
+    #[inline]
+    fn read_exact(&mut self, data: &mut [u8]) -> Result<(), Self::Error> {
+        assert!(self.buffer.is_none());
+        self.reader.read_exact(data)?;
+        self.offset += data.len();
+        Ok(())
+    }
+}
+
+impl<R: Read> Decoder<R> {
+    #[inline]
+    fn pull_title(&mut self) -> Result<Title, Error<R::Error>> {
+        if let Some(title) = self.buffer.take() {
+            self.offset += title.1.as_ref().len() + 1;
+            return Ok(title);
+        }
+
+        let mut prefix = [0u8; 1];
+        self.read_exact(&mut prefix[..])?;
+
+        let major = match prefix[0] >> 5 {
+            0 => Major::Positive,
+            1 => Major::Negative,
+            2 => Major::Bytes,
+            3 => Major::Text,
+            4 => Major::Array,
+            5 => Major::Map,
+            6 => Major::Tag,
+            7 => Major::Other,
+            _ => unreachable!(),
+        };
+
+        let mut minor = match prefix[0] & 0b00011111 {
+            x if x < 24 => Minor::This(x),
+            24 => Minor::Next1([0; 1]),
+            25 => Minor::Next2([0; 2]),
+            26 => Minor::Next4([0; 4]),
+            27 => Minor::Next8([0; 8]),
+            31 => Minor::More,
+            _ => return Err(Error::Syntax(self.offset - 1)),
+        };
+
+        self.read_exact(minor.as_mut())?;
+        Ok(Title(major, minor))
+    }
+
+    #[inline]
+    fn push_title(&mut self, item: Title) {
+        assert!(self.buffer.is_none());
+        self.buffer = Some(item);
+        self.offset -= item.1.as_ref().len() + 1;
+    }
+
+    /// Pulls the next header from the input
+    #[inline]
+    pub fn pull(&mut self) -> Result<Header, Error<R::Error>> {
+        let offset = self.offset;
+        self.pull_title()?
+            .try_into()
+            .map_err(|_| Error::Syntax(offset))
+    }
+
+    /// Push a single header into the input buffer
+    ///
+    /// # Panics
+    ///
+    /// This function panics if called while there is already a header in the
+    /// input buffer. You should take care to call this function only after
+    /// pulling a header to ensure there is nothing in the input buffer.
+    #[inline]
+    pub fn push(&mut self, item: Header) {
+        self.push_title(Title::from(item))
+    }
+
+    /// Gets the current byte offset into the stream
+    ///
+    /// The offset starts at zero when the decoder is created. Therefore, if
+    /// bytes were already read from the reader before the decoder was created,
+    /// you must account for this.
+    #[inline]
+    pub fn offset(&mut self) -> usize {
+        self.offset
+    }
+
+    /// Process an incoming bytes item
+    ///
+    /// In CBOR, bytes can be segmented. The logic for this can be a bit tricky,
+    /// so we encapsulate that logic using this function. This function **MUST**
+    /// be called immediately after first pulling a `Header::Bytes(len)` from
+    /// the wire and `len` must be provided to this function from that value.
+    ///
+    /// The `buf` parameter provides a buffer used when reading in the segmented
+    /// bytes. A large buffer will result in fewer calls to read incoming bytes
+    /// at the cost of memory usage. You should consider this trade off when
+    /// deciding the size of your buffer.
+    #[inline]
+    pub fn bytes(&mut self, len: Option<usize>) -> Segments<R, crate::seg::Bytes> {
+        self.push(Header::Bytes(len));
+        Segments::new(self, |header| match header {
+            Header::Bytes(len) => Ok(len),
+            _ => Err(()),
+        })
+    }
+
+    /// Process an incoming text item
+    ///
+    /// In CBOR, text can be segmented. The logic for this can be a bit tricky,
+    /// so we encapsulate that logic using this function. This function **MUST**
+    /// be called immediately after first pulling a `Header::Text(len)` from
+    /// the wire and `len` must be provided to this function from that value.
+    ///
+    /// The `buf` parameter provides a buffer used when reading in the segmented
+    /// text. A large buffer will result in fewer calls to read incoming bytes
+    /// at the cost of memory usage. You should consider this trade off when
+    /// deciding the size of your buffer.
+    #[inline]
+    pub fn text(&mut self, len: Option<usize>) -> Segments<R, crate::seg::Text> {
+        self.push(Header::Text(len));
+        Segments::new(self, |header| match header {
+            Header::Text(len) => Ok(len),
+            _ => Err(()),
+        })
+    }
+}
diff --git a/src/enc.rs b/src/enc.rs
new file mode 100644
index 0000000..909728f
--- /dev/null
+++ b/src/enc.rs
@@ -0,0 +1,127 @@
+use super::*;
+
+use ciborium_io::Write;
+
+/// An encoder for serializing CBOR items
+///
+/// This structure wraps a writer and provides convenience functions for
+/// writing `Header` objects to the wire.
+pub struct Encoder<W: Write>(W);
+
+impl<W: Write> From<W> for Encoder<W> {
+    #[inline]
+    fn from(value: W) -> Self {
+        Self(value)
+    }
+}
+
+impl<W: Write> Write for Encoder<W> {
+    type Error = W::Error;
+
+    fn write_all(&mut self, data: &[u8]) -> Result<(), Self::Error> {
+        self.0.write_all(data)
+    }
+
+    fn flush(&mut self) -> Result<(), Self::Error> {
+        self.0.flush()
+    }
+}
+
+impl<W: Write> Encoder<W> {
+    /// Push a `Header` to the wire
+    #[inline]
+    pub fn push(&mut self, header: Header) -> Result<(), W::Error> {
+        let title = Title::from(header);
+
+        let major = match title.0 {
+            Major::Positive => 0,
+            Major::Negative => 1,
+            Major::Bytes => 2,
+            Major::Text => 3,
+            Major::Array => 4,
+            Major::Map => 5,
+            Major::Tag => 6,
+            Major::Other => 7,
+        };
+
+        let minor = match title.1 {
+            Minor::This(x) => x,
+            Minor::Next1(..) => 24,
+            Minor::Next2(..) => 25,
+            Minor::Next4(..) => 26,
+            Minor::Next8(..) => 27,
+            Minor::More => 31,
+        };
+
+        self.0.write_all(&[major << 5 | minor])?;
+        self.0.write_all(title.1.as_ref())
+    }
+
+    /// Serialize a byte slice as CBOR
+    ///
+    /// Optionally, segment the output into `segment` size segments. Note that
+    /// if `segment == Some(0)` it will be silently upgraded to `Some(1)`. This
+    /// minimum value is highly inefficient and should not be relied upon.
+    #[inline]
+    pub fn bytes(
+        &mut self,
+        value: &[u8],
+        segment: impl Into<Option<usize>>,
+    ) -> Result<(), W::Error> {
+        let max = segment.into().unwrap_or_else(|| value.len());
+        let max = core::cmp::max(max, 1);
+
+        if max >= value.len() {
+            self.push(Header::Bytes(Some(value.len())))?;
+            self.write_all(value)?;
+        } else {
+            self.push(Header::Bytes(None))?;
+
+            for chunk in value.chunks(max) {
+                self.push(Header::Bytes(Some(chunk.len())))?;
+                self.write_all(chunk)?;
+            }
+
+            self.push(Header::Break)?;
+        }
+
+        Ok(())
+    }
+
+    /// Serialize a string slice as CBOR
+    ///
+    /// Optionally, segment the output into `segment` size segments. Note that
+    /// since care is taken to ensure that each segment is itself a valid UTF-8
+    /// string, if `segment` contains a value of less than 4, it will be
+    /// silently upgraded to 4. This minimum value is highly inefficient and
+    /// should not be relied upon.
+    #[inline]
+    pub fn text(&mut self, value: &str, segment: impl Into<Option<usize>>) -> Result<(), W::Error> {
+        let max = segment.into().unwrap_or_else(|| value.len());
+        let max = core::cmp::max(max, 4);
+
+        if max >= value.len() {
+            self.push(Header::Text(Some(value.len())))?;
+            self.write_all(value.as_bytes())?;
+        } else {
+            self.push(Header::Text(None))?;
+
+            let mut bytes = value.as_bytes();
+            while !bytes.is_empty() {
+                let mut len = core::cmp::min(bytes.len(), max);
+                while len > 0 && core::str::from_utf8(&bytes[..len]).is_err() {
+                    len -= 1
+                }
+
+                let (prefix, suffix) = bytes.split_at(len);
+                self.push(Header::Text(Some(prefix.len())))?;
+                self.write_all(prefix)?;
+                bytes = suffix;
+            }
+
+            self.push(Header::Break)?;
+        }
+
+        Ok(())
+    }
+}
diff --git a/src/hdr.rs b/src/hdr.rs
new file mode 100644
index 0000000..dec1788
--- /dev/null
+++ b/src/hdr.rs
@@ -0,0 +1,163 @@
+use super::*;
+
+use half::f16;
+
+/// A semantic representation of a CBOR item header
+///
+/// This structure represents the valid values of a CBOR item header and is
+/// used extensively when serializing or deserializing CBOR items. Note well
+/// that this structure **DOES NOT** represent the body (i.e. suffix) of the
+/// CBOR item. You must parse the body yourself based on the contents of the
+/// `Header`. However, utility functions are provided for this (see:
+/// `Decoder::bytes()` and `Decoder::text()`).
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub enum Header {
+    /// A positive integer
+    Positive(u64),
+
+    /// A negative integer
+    ///
+    /// Note well that this value has all bits inverted from a normal signed
+    /// integer. For example, to convert the `u64` to a `i128` you would do
+    /// this: `neg as i128 ^ !0`.
+    Negative(u64),
+
+    /// A floating point value
+    Float(f64),
+
+    /// A "simple" value
+    Simple(u8),
+
+    /// A tag
+    Tag(u64),
+
+    /// The "break" value
+    ///
+    /// This value is used to terminate indefinite length arrays and maps,
+    /// as well as segmented byte or text items.
+    Break,
+
+    /// A bytes item
+    ///
+    /// The value contained in this variant indicates the length of the bytes
+    /// which follow or, if `None`, segmented bytes input.
+    ///
+    /// A best practice is to call `Decoder::bytes()` immediately after
+    /// first pulling a bytes item header since this utility function
+    /// encapsulates all the logic needed to handle segmentation.
+    Bytes(Option<usize>),
+
+    /// A text item
+    ///
+    /// The value contained in this variant indicates the length of the text
+    /// which follows (in bytes) or, if `None`, segmented text input.
+    ///
+    /// A best practice is to call `Decoder::text()` immediately after
+    /// first pulling a text item header since this utility function
+    /// encapsulates all the logic needed to handle segmentation.
+    Text(Option<usize>),
+
+    /// An array item
+    ///
+    /// The value contained in this variant indicates the length of the array
+    /// which follows (in items) or, if `None`, an indefinite length array
+    /// terminated by a "break" value.
+    Array(Option<usize>),
+
+    /// An map item
+    ///
+    /// The value contained in this variant indicates the length of the map
+    /// which follows (in item pairs) or, if `None`, an indefinite length map
+    /// terminated by a "break" value.
+    Map(Option<usize>),
+}
+
+impl TryFrom<Title> for Header {
+    type Error = InvalidError;
+
+    fn try_from(title: Title) -> Result<Self, Self::Error> {
+        let opt = |minor| {
+            Some(match minor {
+                Minor::This(x) => x.into(),
+                Minor::Next1(x) => u8::from_be_bytes(x).into(),
+                Minor::Next2(x) => u16::from_be_bytes(x).into(),
+                Minor::Next4(x) => u32::from_be_bytes(x).into(),
+                Minor::Next8(x) => u64::from_be_bytes(x),
+                Minor::More => return None,
+            })
+        };
+
+        let int = |m| opt(m).ok_or(InvalidError(()));
+
+        let len = |m| {
+            opt(m)
+                .map(usize::try_from)
+                .transpose()
+                .or(Err(InvalidError(())))
+        };
+
+        Ok(match title {
+            Title(Major::Positive, minor) => Self::Positive(int(minor)?),
+            Title(Major::Negative, minor) => Self::Negative(int(minor)?),
+            Title(Major::Bytes, minor) => Self::Bytes(len(minor)?),
+            Title(Major::Text, minor) => Self::Text(len(minor)?),
+            Title(Major::Array, minor) => Self::Array(len(minor)?),
+            Title(Major::Map, minor) => Self::Map(len(minor)?),
+            Title(Major::Tag, minor) => Self::Tag(int(minor)?),
+
+            Title(Major::Other, Minor::More) => Self::Break,
+            Title(Major::Other, Minor::This(x)) => Self::Simple(x),
+            Title(Major::Other, Minor::Next1(x)) => Self::Simple(x[0]),
+            Title(Major::Other, Minor::Next2(x)) => Self::Float(f16::from_be_bytes(x).into()),
+            Title(Major::Other, Minor::Next4(x)) => Self::Float(f32::from_be_bytes(x).into()),
+            Title(Major::Other, Minor::Next8(x)) => Self::Float(f64::from_be_bytes(x)),
+        })
+    }
+}
+
+impl From<Header> for Title {
+    fn from(header: Header) -> Self {
+        let int = |i: u64| match i {
+            x if x <= 23 => Minor::This(i as u8),
+            x if x <= core::u8::MAX as u64 => Minor::Next1([i as u8]),
+            x if x <= core::u16::MAX as u64 => Minor::Next2((i as u16).to_be_bytes()),
+            x if x <= core::u32::MAX as u64 => Minor::Next4((i as u32).to_be_bytes()),
+            x => Minor::Next8(x.to_be_bytes()),
+        };
+
+        let len = |l: Option<usize>| l.map(|x| int(x as u64)).unwrap_or(Minor::More);
+
+        match header {
+            Header::Positive(x) => Title(Major::Positive, int(x)),
+            Header::Negative(x) => Title(Major::Negative, int(x)),
+            Header::Bytes(x) => Title(Major::Bytes, len(x)),
+            Header::Text(x) => Title(Major::Text, len(x)),
+            Header::Array(x) => Title(Major::Array, len(x)),
+            Header::Map(x) => Title(Major::Map, len(x)),
+            Header::Tag(x) => Title(Major::Tag, int(x)),
+
+            Header::Break => Title(Major::Other, Minor::More),
+
+            Header::Simple(x) => match x {
+                x @ 0..=23 => Title(Major::Other, Minor::This(x)),
+                x => Title(Major::Other, Minor::Next1([x])),
+            },
+
+            Header::Float(n64) => {
+                let n16 = f16::from_f64(n64);
+                let n32 = n64 as f32;
+
+                Title(
+                    Major::Other,
+                    if f64::from(n16).to_bits() == n64.to_bits() {
+                        Minor::Next2(n16.to_be_bytes())
+                    } else if f64::from(n32).to_bits() == n64.to_bits() {
+                        Minor::Next4(n32.to_be_bytes())
+                    } else {
+                        Minor::Next8(n64.to_be_bytes())
+                    },
+                )
+            }
+        }
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..8a1fe90
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,487 @@
+// SPDX-License-Identifier: Apache-2.0
+
+//! Low level CBOR parsing tools
+//!
+//! This crate contains low-level types for encoding and decoding items in
+//! CBOR. This crate is usable in both `no_std` and `no_alloc` environments.
+//! To understand how this crate works, first we will look at the structure
+//! of a CBOR item on the wire.
+//!
+//! # Anatomy of a CBOR Item
+//!
+//! This is a brief anatomy of a CBOR item on the wire.
+//!
+//! ```text
+//! +------------+-----------+
+//! |            |           |
+//! |   Major    |   Minor   |
+//! |  (3bits)   |  (5bits)  |
+//! |            |           |
+//! +------------+-----------+
+//! ^                        ^
+//! |                        |
+//! +-----+            +-----+
+//!       |            |
+//!       |            |
+//!       +----------------------------+--------------+
+//!       |            |               |              |
+//!       |   Prefix   |     Affix     |    Suffix    |
+//!       |  (1 byte)  |  (0-8 bytes)  |  (0+ bytes)  |
+//!       |            |               |              |
+//!       +------------+---------------+--------------+
+//!
+//!       |                            |              |
+//!       +------------+---------------+--------------+
+//!                    |                       |
+//!                    v                       v
+//!
+//!                  Header                   Body
+//! ```
+//!
+//! The `ciborium` crate works by providing the `Decoder` and `Encoder` types
+//! which provide input and output for a CBOR header (see: `Header`). From
+//! there, you can either handle the body yourself or use the provided utility
+//! functions.
+//!
+//! For more information on the CBOR format, see
+//! [RFC 7049](https://tools.ietf.org/html/rfc7049).
+//!
+//! # Decoding
+//!
+//! In order to decode CBOR, you will create a `Decoder` from a reader. The
+//! decoder instance will allow you to `Decoder::pull()` `Header` instances
+//! from the input.
+//!
+//! Most CBOR items are fully contained in their headers and therefore have no
+//! body. These items can be evaluated directly from the `Header` instance.
+//!
+//! Bytes and text items have a body but do not contain child items. Since
+//! both bytes and text values may be segmented, parsing them can be a bit
+//! tricky. Therefore, we provide helper functions to parse these types. See
+//! `Decoder::bytes()` and `Decoder::text()` for more details.
+//!
+//! Array and map items have a body which contains child items. These can be
+//! parsed by simply doing `Decoder::pull()` to parse the child items.
+//!
+//! ## Example
+//!
+//! ```rust
+//! use ciborium_ll::{Decoder, Header};
+//! use ciborium_io::Read as _;
+//!
+//! let input = b"\x6dHello, World!";
+//! let mut decoder = Decoder::from(&input[..]);
+//! let mut chunks = 0;
+//!
+//! match decoder.pull().unwrap() {
+//!     Header::Text(len) => {
+//!         let mut segments = decoder.text(len);
+//!         while let Some(mut segment) = segments.pull().unwrap() {
+//!             let mut buffer = [0u8; 7];
+//!             while let Some(chunk) = segment.pull(&mut buffer[..]).unwrap() {
+//!                  match chunk {
+//!                      "Hello, " if chunks == 0 => chunks = 1,
+//!                      "World!" if chunks == 1 => chunks = 2,
+//!                      _ => panic!("received unexpected chunk"),
+//!                  }
+//!             }
+//!         }
+//!     }
+//!
+//!     _ => panic!("received unexpected value"),
+//! }
+//!
+//! assert_eq!(chunks, 2);
+//! ```
+//!
+//! # Encoding
+//!
+//! To encode values to CBOR, create an `Encoder` from a writer. The encoder
+//! instance provides the `Encoder::push()` method to write a `Header` value
+//! to the wire. CBOR item bodies can be written directly.
+//!
+//! For bytes and text, there are the `Encoder::bytes()` and `Encoder::text()`
+//! utility functions, respectively, which will properly segment the output
+//! on the wire for you.
+//!
+//! ## Example
+//!
+//! ```rust
+//! use ciborium_ll::{Encoder, Header};
+//! use ciborium_io::Write as _;
+//!
+//! let mut buffer = [0u8; 19];
+//! let mut encoder = Encoder::from(&mut buffer[..]);
+//!
+//! // Write the structure
+//! encoder.push(Header::Map(Some(1))).unwrap();
+//! encoder.push(Header::Positive(7)).unwrap();
+//! encoder.text("Hello, World!", 7).unwrap();
+//!
+//! // Validate our output
+//! encoder.flush().unwrap();
+//! assert_eq!(b"\xa1\x07\x7f\x67Hello, \x66World!\xff", &buffer[..]);
+//! ```
+
+#![cfg_attr(not(feature = "std"), no_std)]
+#![deny(missing_docs)]
+#![deny(clippy::all)]
+#![deny(clippy::cargo)]
+
+#[cfg(feature = "alloc")]
+extern crate alloc;
+
+mod dec;
+mod enc;
+mod hdr;
+mod seg;
+
+pub use dec::*;
+pub use enc::*;
+pub use hdr::*;
+pub use seg::{Segment, Segments};
+
+/// Simple value constants
+pub mod simple {
+    #![allow(missing_docs)]
+
+    pub const FALSE: u8 = 20;
+    pub const TRUE: u8 = 21;
+    pub const NULL: u8 = 22;
+    pub const UNDEFINED: u8 = 23;
+}
+
+/// Tag constants
+pub mod tag {
+    #![allow(missing_docs)]
+
+    pub const BIGPOS: u64 = 2;
+    pub const BIGNEG: u64 = 3;
+}
+
+#[derive(Debug)]
+struct InvalidError(());
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum Major {
+    Positive,
+    Negative,
+    Bytes,
+    Text,
+    Array,
+    Map,
+    Tag,
+    Other,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum Minor {
+    This(u8),
+    Next1([u8; 1]),
+    Next2([u8; 2]),
+    Next4([u8; 4]),
+    Next8([u8; 8]),
+    More,
+}
+
+impl AsRef<[u8]> for Minor {
+    #[inline]
+    fn as_ref(&self) -> &[u8] {
+        match self {
+            Self::More => &[],
+            Self::This(..) => &[],
+            Self::Next1(x) => x.as_ref(),
+            Self::Next2(x) => x.as_ref(),
+            Self::Next4(x) => x.as_ref(),
+            Self::Next8(x) => x.as_ref(),
+        }
+    }
+}
+
+impl AsMut<[u8]> for Minor {
+    #[inline]
+    fn as_mut(&mut self) -> &mut [u8] {
+        match self {
+            Self::More => &mut [],
+            Self::This(..) => &mut [],
+            Self::Next1(x) => x.as_mut(),
+            Self::Next2(x) => x.as_mut(),
+            Self::Next4(x) => x.as_mut(),
+            Self::Next8(x) => x.as_mut(),
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+struct Title(pub Major, pub Minor);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    macro_rules! neg {
+        ($i:expr) => {
+            Header::Negative((($i as i128) ^ !0) as u64)
+        };
+    }
+
+    #[allow(clippy::excessive_precision)]
+    #[test]
+    fn leaf() {
+        use core::f64::{INFINITY, NAN};
+
+        let data = &[
+            (Header::Positive(0), "00", true),
+            (Header::Positive(1), "01", true),
+            (Header::Positive(10), "0a", true),
+            (Header::Positive(23), "17", true),
+            (Header::Positive(24), "1818", true),
+            (Header::Positive(25), "1819", true),
+            (Header::Positive(100), "1864", true),
+            (Header::Positive(1000), "1903e8", true),
+            (Header::Positive(1000000), "1a000f4240", true),
+            (Header::Positive(1000000000000), "1b000000e8d4a51000", true),
+            (
+                Header::Positive(18446744073709551615),
+                "1bffffffffffffffff",
+                true,
+            ),
+            (neg!(-18446744073709551616), "3bffffffffffffffff", true),
+            (neg!(-1), "20", true),
+            (neg!(-10), "29", true),
+            (neg!(-100), "3863", true),
+            (neg!(-1000), "3903e7", true),
+            (Header::Float(0.0), "f90000", true),
+            (Header::Float(-0.0), "f98000", true),
+            (Header::Float(1.0), "f93c00", true),
+            (Header::Float(1.1), "fb3ff199999999999a", true),
+            (Header::Float(1.5), "f93e00", true),
+            (Header::Float(65504.0), "f97bff", true),
+            (Header::Float(100000.0), "fa47c35000", true),
+            (Header::Float(3.4028234663852886e+38), "fa7f7fffff", true),
+            (Header::Float(1.0e+300), "fb7e37e43c8800759c", true),
+            (Header::Float(5.960464477539063e-8), "f90001", true),
+            (Header::Float(0.00006103515625), "f90400", true),
+            (Header::Float(-4.0), "f9c400", true),
+            (Header::Float(-4.1), "fbc010666666666666", true),
+            (Header::Float(INFINITY), "f97c00", true),
+            (Header::Float(NAN), "f97e00", true),
+            (Header::Float(-INFINITY), "f9fc00", true),
+            (Header::Float(INFINITY), "fa7f800000", false),
+            (Header::Float(NAN), "fa7fc00000", false),
+            (Header::Float(-INFINITY), "faff800000", false),
+            (Header::Float(INFINITY), "fb7ff0000000000000", false),
+            (Header::Float(NAN), "fb7ff8000000000000", false),
+            (Header::Float(-INFINITY), "fbfff0000000000000", false),
+            (Header::Simple(simple::FALSE), "f4", true),
+            (Header::Simple(simple::TRUE), "f5", true),
+            (Header::Simple(simple::NULL), "f6", true),
+            (Header::Simple(simple::UNDEFINED), "f7", true),
+            (Header::Simple(16), "f0", true),
+            (Header::Simple(24), "f818", true),
+            (Header::Simple(255), "f8ff", true),
+            (Header::Tag(0), "c0", true),
+            (Header::Tag(1), "c1", true),
+            (Header::Tag(23), "d7", true),
+            (Header::Tag(24), "d818", true),
+            (Header::Tag(32), "d820", true),
+            (Header::Bytes(Some(0)), "40", true),
+            (Header::Bytes(Some(4)), "44", true),
+            (Header::Text(Some(0)), "60", true),
+            (Header::Text(Some(4)), "64", true),
+        ];
+
+        for (header, bytes, encode) in data.iter().cloned() {
+            let bytes = hex::decode(bytes).unwrap();
+
+            let mut decoder = Decoder::from(&bytes[..]);
+            match (header, decoder.pull().unwrap()) {
+                // NaN equality...
+                (Header::Float(l), Header::Float(r)) if l.is_nan() && r.is_nan() => (),
+
+                // Everything else...
+                (l, r) => assert_eq!(l, r),
+            }
+
+            if encode {
+                let mut buffer = [0u8; 1024];
+                let mut writer = &mut buffer[..];
+                let mut encoder = Encoder::from(&mut writer);
+                encoder.push(header).unwrap();
+
+                let len = writer.len();
+                assert_eq!(&bytes[..], &buffer[..1024 - len]);
+            }
+        }
+    }
+
+    #[test]
+    fn node() {
+        let data: &[(&str, &[Header])] = &[
+            ("80", &[Header::Array(Some(0))]),
+            (
+                "83010203",
+                &[
+                    Header::Array(Some(3)),
+                    Header::Positive(1),
+                    Header::Positive(2),
+                    Header::Positive(3),
+                ],
+            ),
+            (
+                "98190102030405060708090a0b0c0d0e0f101112131415161718181819",
+                &[
+                    Header::Array(Some(25)),
+                    Header::Positive(1),
+                    Header::Positive(2),
+                    Header::Positive(3),
+                    Header::Positive(4),
+                    Header::Positive(5),
+                    Header::Positive(6),
+                    Header::Positive(7),
+                    Header::Positive(8),
+                    Header::Positive(9),
+                    Header::Positive(10),
+                    Header::Positive(11),
+                    Header::Positive(12),
+                    Header::Positive(13),
+                    Header::Positive(14),
+                    Header::Positive(15),
+                    Header::Positive(16),
+                    Header::Positive(17),
+                    Header::Positive(18),
+                    Header::Positive(19),
+                    Header::Positive(20),
+                    Header::Positive(21),
+                    Header::Positive(22),
+                    Header::Positive(23),
+                    Header::Positive(24),
+                    Header::Positive(25),
+                ],
+            ),
+            ("a0", &[Header::Map(Some(0))]),
+            (
+                "a201020304",
+                &[
+                    Header::Map(Some(2)),
+                    Header::Positive(1),
+                    Header::Positive(2),
+                    Header::Positive(3),
+                    Header::Positive(4),
+                ],
+            ),
+            ("9fff", &[Header::Array(None), Header::Break]),
+            (
+                "9f018202039f0405ffff",
+                &[
+                    Header::Array(None),
+                    Header::Positive(1),
+                    Header::Array(Some(2)),
+                    Header::Positive(2),
+                    Header::Positive(3),
+                    Header::Array(None),
+                    Header::Positive(4),
+                    Header::Positive(5),
+                    Header::Break,
+                    Header::Break,
+                ],
+            ),
+            (
+                "9f01820203820405ff",
+                &[
+                    Header::Array(None),
+                    Header::Positive(1),
+                    Header::Array(Some(2)),
+                    Header::Positive(2),
+                    Header::Positive(3),
+                    Header::Array(Some(2)),
+                    Header::Positive(4),
+                    Header::Positive(5),
+                    Header::Break,
+                ],
+            ),
+            (
+                "83018202039f0405ff",
+                &[
+                    Header::Array(Some(3)),
+                    Header::Positive(1),
+                    Header::Array(Some(2)),
+                    Header::Positive(2),
+                    Header::Positive(3),
+                    Header::Array(None),
+                    Header::Positive(4),
+                    Header::Positive(5),
+                    Header::Break,
+                ],
+            ),
+            (
+                "83019f0203ff820405",
+                &[
+                    Header::Array(Some(3)),
+                    Header::Positive(1),
+                    Header::Array(None),
+                    Header::Positive(2),
+                    Header::Positive(3),
+                    Header::Break,
+                    Header::Array(Some(2)),
+                    Header::Positive(4),
+                    Header::Positive(5),
+                ],
+            ),
+            (
+                "9f0102030405060708090a0b0c0d0e0f101112131415161718181819ff",
+                &[
+                    Header::Array(None),
+                    Header::Positive(1),
+                    Header::Positive(2),
+                    Header::Positive(3),
+                    Header::Positive(4),
+                    Header::Positive(5),
+                    Header::Positive(6),
+                    Header::Positive(7),
+                    Header::Positive(8),
+                    Header::Positive(9),
+                    Header::Positive(10),
+                    Header::Positive(11),
+                    Header::Positive(12),
+                    Header::Positive(13),
+                    Header::Positive(14),
+                    Header::Positive(15),
+                    Header::Positive(16),
+                    Header::Positive(17),
+                    Header::Positive(18),
+                    Header::Positive(19),
+                    Header::Positive(20),
+                    Header::Positive(21),
+                    Header::Positive(22),
+                    Header::Positive(23),
+                    Header::Positive(24),
+                    Header::Positive(25),
+                    Header::Break,
+                ],
+            ),
+        ];
+
+        for (bytes, headers) in data {
+            let bytes = hex::decode(bytes).unwrap();
+
+            // Test decoding
+            let mut decoder = Decoder::from(&bytes[..]);
+            for header in headers.iter().cloned() {
+                assert_eq!(header, decoder.pull().unwrap());
+            }
+
+            // Test encoding
+            let mut buffer = [0u8; 1024];
+            let mut writer = &mut buffer[..];
+            let mut encoder = Encoder::from(&mut writer);
+
+            for header in headers.iter().cloned() {
+                encoder.push(header).unwrap();
+            }
+
+            let len = writer.len();
+            assert_eq!(&bytes[..], &buffer[..1024 - len]);
+        }
+    }
+}
diff --git a/src/seg.rs b/src/seg.rs
new file mode 100644
index 0000000..d75ebae
--- /dev/null
+++ b/src/seg.rs
@@ -0,0 +1,213 @@
+use super::*;
+
+use ciborium_io::Read;
+
+use core::marker::PhantomData;
+
+/// A parser for incoming segments
+pub trait Parser: Default {
+    /// The type of item that is parsed
+    type Item: ?Sized;
+
+    /// The parsing error that may occur
+    type Error;
+
+    /// The main parsing function
+    ///
+    /// This function processes the incoming bytes and returns the item.
+    ///
+    /// One important detail that **MUST NOT** be overlooked is that the
+    /// parser may save data from a previous parsing attempt. The number of
+    /// bytes saved is indicated by the `Parser::saved()` function. The saved
+    /// bytes will be copied into the beginning of the `bytes` array before
+    /// processing. Therefore, two requirements should be met.
+    ///
+    /// First, the incoming byte slice should be larger than the saved bytes.
+    ///
+    /// Second, the incoming byte slice should contain new bytes only after
+    /// the saved byte prefix.
+    ///
+    /// If both criteria are met, this allows the parser to prepend its saved
+    /// bytes without any additional allocation.
+    fn parse<'a>(&mut self, bytes: &'a mut [u8]) -> Result<&'a Self::Item, Self::Error>;
+
+    /// Indicates the number of saved bytes in the parser
+    fn saved(&self) -> usize {
+        0
+    }
+}
+
+/// A bytes parser
+///
+/// No actual processing is performed and the input bytes are directly
+/// returned. This implies that this parser never saves any bytes internally.
+#[derive(Default)]
+pub struct Bytes(());
+
+impl Parser for Bytes {
+    type Item = [u8];
+    type Error = core::convert::Infallible;
+
+    fn parse<'a>(&mut self, bytes: &'a mut [u8]) -> Result<&'a [u8], Self::Error> {
+        Ok(bytes)
+    }
+}
+
+/// A text parser
+///
+/// This parser converts the input bytes to a `str`. This parser preserves
+/// trailing invalid UTF-8 sequences in the case that chunking fell in the
+/// middle of a valid UTF-8 character.
+#[derive(Default)]
+pub struct Text {
+    stored: usize,
+    buffer: [u8; 3],
+}
+
+impl Parser for Text {
+    type Item = str;
+    type Error = core::str::Utf8Error;
+
+    fn parse<'a>(&mut self, bytes: &'a mut [u8]) -> Result<&'a str, Self::Error> {
+        // If we cannot advance, return nothing.
+        if bytes.len() <= self.stored {
+            return Ok("");
+        }
+
+        // Copy previously invalid data into place.
+        bytes[..self.stored].clone_from_slice(&self.buffer[..self.stored]);
+
+        Ok(match core::str::from_utf8(bytes) {
+            Ok(s) => s,
+            Err(e) => {
+                let valid_len = e.valid_up_to();
+                let invalid_len = bytes.len() - valid_len;
+
+                // If the size of the invalid UTF-8 is large enough to hold
+                // all valid UTF-8 characters, we have a syntax error.
+                if invalid_len > self.buffer.len() {
+                    return Err(e);
+                }
+
+                // Otherwise, store the invalid bytes for the next read cycle.
+                self.buffer[..invalid_len].clone_from_slice(&bytes[valid_len..]);
+                self.stored = invalid_len;
+
+                // Decode the valid part of the string.
+                core::str::from_utf8(&bytes[..valid_len]).unwrap()
+            }
+        })
+    }
+
+    fn saved(&self) -> usize {
+        self.stored
+    }
+}
+
+/// A CBOR segment
+///
+/// This type represents a single bytes or text segment on the wire. It can be
+/// read out in parsed chunks based on the size of the input scratch buffer.
+pub struct Segment<'r, R: Read, P: Parser> {
+    reader: &'r mut Decoder<R>,
+    unread: usize,
+    offset: usize,
+    parser: P,
+}
+
+impl<'r, R: Read, P: Parser> Segment<'r, R, P> {
+    /// Gets the number of unprocessed bytes
+    #[inline]
+    pub fn left(&self) -> usize {
+        self.unread + self.parser.saved()
+    }
+
+    /// Gets the next parsed chunk within the segment
+    ///
+    /// Returns `Ok(None)` when all chunks have been read.
+    #[inline]
+    pub fn pull<'a>(
+        &mut self,
+        buffer: &'a mut [u8],
+    ) -> Result<Option<&'a P::Item>, Error<R::Error>> {
+        use core::cmp::min;
+
+        let prev = self.parser.saved();
+        match self.unread {
+            0 if prev == 0 => return Ok(None),
+            0 => return Err(Error::Syntax(self.offset)),
+            _ => (),
+        }
+
+        // Determine how many bytes to read.
+        let size = min(buffer.len(), prev + self.unread);
+        let full = &mut buffer[..size];
+        let next = &mut full[min(size, prev)..];
+
+        // Read additional bytes.
+        self.reader.read_exact(next)?;
+        self.unread -= next.len();
+
+        self.parser
+            .parse(full)
+            .or(Err(Error::Syntax(self.offset)))
+            .map(Some)
+    }
+}
+
+/// A sequence of CBOR segments
+///
+/// CBOR allows for bytes or text items to be segmented. This type represents
+/// the state of that segmented input stream.
+pub struct Segments<'r, R: Read, P: Parser> {
+    reader: &'r mut Decoder<R>,
+    finish: bool,
+    nested: usize,
+    parser: PhantomData<P>,
+    unwrap: fn(Header) -> Result<Option<usize>, ()>,
+}
+
+impl<'r, R: Read, P: Parser> Segments<'r, R, P> {
+    #[inline]
+    pub(crate) fn new(
+        decoder: &'r mut Decoder<R>,
+        unwrap: fn(Header) -> Result<Option<usize>, ()>,
+    ) -> Self {
+        Self {
+            reader: decoder,
+            finish: false,
+            nested: 0,
+            parser: PhantomData,
+            unwrap,
+        }
+    }
+
+    /// Gets the next segment in the stream
+    ///
+    /// Returns `Ok(None)` at the conclusion of the stream.
+    #[inline]
+    pub fn pull(&mut self) -> Result<Option<Segment<R, P>>, Error<R::Error>> {
+        while !self.finish {
+            let offset = self.reader.offset();
+            match self.reader.pull()? {
+                Header::Break if self.nested == 1 => return Ok(None),
+                Header::Break if self.nested > 1 => self.nested -= 1,
+                header => match (self.unwrap)(header) {
+                    Err(..) => return Err(Error::Syntax(offset)),
+                    Ok(None) => self.nested += 1,
+                    Ok(Some(len)) => {
+                        self.finish = self.nested == 0;
+                        return Ok(Some(Segment {
+                            reader: self.reader,
+                            unread: len,
+                            offset,
+                            parser: P::default(),
+                        }));
+                    }
+                },
+            }
+        }
+
+        Ok(None)
+    }
+}