diff options
Diffstat (limited to 'pw_varint/public/pw_varint/varint.h')
| -rw-r--r-- | pw_varint/public/pw_varint/varint.h | 104 |
1 files changed, 91 insertions, 13 deletions
diff --git a/pw_varint/public/pw_varint/varint.h b/pw_varint/public/pw_varint/varint.h index a8db949cc..9d0e0ce49 100644 --- a/pw_varint/public/pw_varint/varint.h +++ b/pw_varint/public/pw_varint/varint.h @@ -24,17 +24,47 @@ extern "C" { // Expose a subset of the varint API for use in C code. -size_t pw_VarintEncode(uint64_t integer, void* output, size_t output_size); -size_t pw_VarintZigZagEncode(int64_t integer, void* output, size_t output_size); +typedef enum { + PW_VARINT_ZERO_TERMINATED_LEAST_SIGNIFICANT = 0b00, + PW_VARINT_ZERO_TERMINATED_MOST_SIGNIFICANT = 0b01, + PW_VARINT_ONE_TERMINATED_LEAST_SIGNIFICANT = 0b10, + PW_VARINT_ONE_TERMINATED_MOST_SIGNIFICANT = 0b11, +} pw_varint_Format; + +size_t pw_varint_EncodeCustom(uint64_t integer, + void* output, + size_t output_size, + pw_varint_Format format); +size_t pw_varint_DecodeCustom(const void* input, + size_t input_size, + uint64_t* output, + pw_varint_Format format); + +static inline size_t pw_varint_Encode(uint64_t integer, + void* output, + size_t output_size) { + return pw_varint_EncodeCustom( + integer, output, output_size, PW_VARINT_ZERO_TERMINATED_MOST_SIGNIFICANT); +} + +size_t pw_varint_ZigZagEncode(int64_t integer, + void* output, + size_t output_size); + +static inline size_t pw_varint_Decode(const void* input, + size_t input_size, + uint64_t* output) { + return pw_varint_DecodeCustom( + input, input_size, output, PW_VARINT_ZERO_TERMINATED_MOST_SIGNIFICANT); +} -size_t pw_VarintDecode(const void* input, size_t input_size, uint64_t* output); -size_t pw_VarintZigZagDecode(const void* input, - size_t input_size, - int64_t* output); +size_t pw_varint_ZigZagDecode(const void* input, + size_t input_size, + int64_t* output); // Returns the size of an when encoded as a varint. -size_t pw_VarintEncodedSize(uint64_t integer); -size_t pw_VarintZigZagEncodedSize(int64_t integer); +size_t pw_varint_EncodedSize(uint64_t integer); +size_t pw_varint_ZigZagEncodedSize(int64_t integer); #ifdef __cplusplus @@ -83,7 +113,7 @@ constexpr std::make_signed_t<T> ZigZagDecode(T n) // Encodes a uint64_t with Little-Endian Base 128 (LEB128) encoding. inline size_t EncodeLittleEndianBase128(uint64_t integer, const std::span<std::byte>& output) { - return pw_VarintEncode(integer, output.data(), output.size()); + return pw_varint_Encode(integer, output.data(), output.size()); } // Encodes the provided integer using a variable-length encoding and returns the @@ -99,9 +129,9 @@ inline size_t EncodeLittleEndianBase128(uint64_t integer, template <typename T> size_t Encode(T integer, const std::span<std::byte>& output) { if (std::is_signed<T>()) { - return pw_VarintZigZagEncode(integer, output.data(), output.size()); + return pw_varint_ZigZagEncode(integer, output.data(), output.size()); } else { - return pw_VarintEncode(integer, output.data(), output.size()); + return pw_varint_Encode(integer, output.data(), output.size()); } } @@ -126,11 +156,36 @@ size_t Encode(T integer, const std::span<std::byte>& output) { // } // inline size_t Decode(const std::span<const std::byte>& input, int64_t* value) { - return pw_VarintZigZagDecode(input.data(), input.size(), value); + return pw_varint_ZigZagDecode(input.data(), input.size(), value); } inline size_t Decode(const std::span<const std::byte>& input, uint64_t* value) { - return pw_VarintDecode(input.data(), input.size(), value); + return pw_varint_Decode(input.data(), input.size(), value); +} + +enum class Format { + kZeroTerminatedLeastSignificant = PW_VARINT_ZERO_TERMINATED_LEAST_SIGNIFICANT, + kZeroTerminatedMostSignificant = PW_VARINT_ZERO_TERMINATED_MOST_SIGNIFICANT, + kOneTerminatedLeastSignificant = PW_VARINT_ONE_TERMINATED_LEAST_SIGNIFICANT, + kOneTerminatedMostSignificant = PW_VARINT_ONE_TERMINATED_MOST_SIGNIFICANT, +}; + +// Encodes a varint in a custom format. +inline size_t Encode(uint64_t value, + std::span<std::byte> output, + Format format) { + return pw_varint_EncodeCustom(value, + output.data(), + output.size(), + static_cast<pw_varint_Format>(format)); +} + +// Decodes a varint from a custom format. +inline size_t Decode(std::span<const std::byte> input, + uint64_t* value, + Format format) { + return pw_varint_DecodeCustom( + input.data(), input.size(), value, static_cast<pw_varint_Format>(format)); } // Returns a size of an integer when encoded as a varint. @@ -143,6 +198,29 @@ constexpr size_t ZigZagEncodedSize(int64_t integer) { return EncodedSize(ZigZagEncode(integer)); } +// Returns the maximum integer value that can be encoded in a varint of the +// specified number of bytes. +// +// These values are also listed in the table below. Zigzag encoding cuts these +// in half, as positive and negative integers are alternated. +// +// Bytes Max value +// 1 127 +// 2 16,383 +// 3 2,097,151 +// 4 268,435,455 +// 5 34,359,738,367 -- needed for max uint32 value +// 6 4,398,046,511,103 +// 7 562,949,953,421,311 +// 8 72,057,594,037,927,935 +// 9 9,223,372,036,854,775,807 +// 10 uint64 max value +// +constexpr uint64_t MaxValueInBytes(size_t bytes) { + return bytes >= kMaxVarint64SizeBytes ? std::numeric_limits<uint64_t>::max() + : (uint64_t(1) << (7 * bytes)) - 1; +} + } // namespace varint } // namespace pw |