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diff --git a/src/common.rs b/src/common.rs
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+// Translated from C to Rust. The original C code can be found at
+// https://github.com/ulfjack/ryu and carries the following license:
+//
+// Copyright 2018 Ulf Adams
+//
+// The contents of this file may be used under the terms of the Apache License,
+// Version 2.0.
+//
+//    (See accompanying file LICENSE-Apache or copy at
+//     http://www.apache.org/licenses/LICENSE-2.0)
+//
+// Alternatively, the contents of this file may be used under the terms of
+// the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE-Boost or copy at
+//     https://www.boost.org/LICENSE_1_0.txt)
+//
+// Unless required by applicable law or agreed to in writing, this software
+// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.
+
+// Returns the number of decimal digits in v, which must not contain more than 9
+// digits.
+#[cfg_attr(feature = "no-panic", inline)]
+pub fn decimal_length9(v: u32) -> u32 {
+    // Function precondition: v is not a 10-digit number.
+    // (f2s: 9 digits are sufficient for round-tripping.)
+    debug_assert!(v < 1000000000);
+
+    if v >= 100000000 {
+        9
+    } else if v >= 10000000 {
+        8
+    } else if v >= 1000000 {
+        7
+    } else if v >= 100000 {
+        6
+    } else if v >= 10000 {
+        5
+    } else if v >= 1000 {
+        4
+    } else if v >= 100 {
+        3
+    } else if v >= 10 {
+        2
+    } else {
+        1
+    }
+}
+
+// Returns e == 0 ? 1 : [log_2(5^e)]; requires 0 <= e <= 3528.
+#[cfg_attr(feature = "no-panic", inline)]
+#[allow(dead_code)]
+pub fn log2_pow5(e: i32) -> i32 /* or u32 -> u32 */ {
+    // This approximation works up to the point that the multiplication
+    // overflows at e = 3529. If the multiplication were done in 64 bits, it
+    // would fail at 5^4004 which is just greater than 2^9297.
+    debug_assert!(e >= 0);
+    debug_assert!(e <= 3528);
+    ((e as u32 * 1217359) >> 19) as i32
+}
+
+// Returns e == 0 ? 1 : ceil(log_2(5^e)); requires 0 <= e <= 3528.
+#[cfg_attr(feature = "no-panic", inline)]
+pub fn pow5bits(e: i32) -> i32 /* or u32 -> u32 */ {
+    // This approximation works up to the point that the multiplication
+    // overflows at e = 3529. If the multiplication were done in 64 bits, it
+    // would fail at 5^4004 which is just greater than 2^9297.
+    debug_assert!(e >= 0);
+    debug_assert!(e <= 3528);
+    (((e as u32 * 1217359) >> 19) + 1) as i32
+}
+
+#[cfg_attr(feature = "no-panic", inline)]
+#[allow(dead_code)]
+pub fn ceil_log2_pow5(e: i32) -> i32 /* or u32 -> u32 */ {
+    log2_pow5(e) + 1
+}
+
+// Returns floor(log_10(2^e)); requires 0 <= e <= 1650.
+#[cfg_attr(feature = "no-panic", inline)]
+pub fn log10_pow2(e: i32) -> u32 /* or u32 -> u32 */ {
+    // The first value this approximation fails for is 2^1651 which is just greater than 10^297.
+    debug_assert!(e >= 0);
+    debug_assert!(e <= 1650);
+    (e as u32 * 78913) >> 18
+}
+
+// Returns floor(log_10(5^e)); requires 0 <= e <= 2620.
+#[cfg_attr(feature = "no-panic", inline)]
+pub fn log10_pow5(e: i32) -> u32 /* or u32 -> u32 */ {
+    // The first value this approximation fails for is 5^2621 which is just greater than 10^1832.
+    debug_assert!(e >= 0);
+    debug_assert!(e <= 2620);
+    (e as u32 * 732923) >> 20
+}