zmij

Author: dtolnay

.gitignore

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+/target
+/Cargo.lock

Cargo.toml

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+[package]
+name = "zmij"
+version = "0.0.1"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+categories = ["value-formatting", "no-std", "no-std::no-alloc"]
+description = "A double-to-string conversion algorithm based on Schubfach and yy"
+documentation = "https://docs.rs/zmij"
+edition = "2024"
+license = "MIT"
+
+[workspace]
+members = ["gen-pow10"]
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+rustdoc-args = [
+    "--generate-link-to-definition",
+    "--generate-macro-expansion",
+    "--extern-html-root-url=core=https://doc.rust-lang.org",
+]

LICENSE

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+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

gen-pow10/Cargo.toml

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+[package]
+name = "gen-pow10"
+version = "0.0.0"
+edition = "2024"
+publish = false
+
+[[bin]]
+name = "gen-pow10"
+path = "main.rs"
+
+[dependencies]
+num-bigint = "0.4"
+num-integer = "0.1"

gen-pow10/main.rs

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+// Power of 10 overestimates generator for the Schubfach algorithm:
+// https://fmt.dev/papers/Schubfach4.pdf.
+// Copyright (c) 2025 - present, Victor Zverovich
+
+use num_bigint::BigUint as Uint;
+use num_integer::Integer as _;
+use std::f64::consts::LOG2_10;
+
+fn main() {
+    // Range of decimal exponents [K_min, K_max] from the paper.
+    let dec_exp_min = -324_i32;
+    let dec_exp_max = 292_i32;
+
+    let num_bits = 128_i32;
+
+    // Negate dec_pow_min and dec_pow_max because we need negative powers 10^-k.
+    for dec_exp in -dec_exp_max..=-dec_exp_min {
+        // dec_exp is -k in the paper.
+        let bin_exp = (f64::from(dec_exp) * LOG2_10).floor() as i32 - (num_bits - 1);
+        let bin_pow = Uint::from(2_u8).pow(bin_exp.unsigned_abs());
+        let dec_pow = Uint::from(10_u8).pow(dec_exp.unsigned_abs());
+        let mut result = if dec_exp < 0 {
+            bin_pow / dec_pow
+        } else if bin_exp < 0 {
+            dec_pow * bin_pow
+        } else {
+            dec_pow / bin_pow
+        };
+        result.inc();
+        let hi = &result >> 64;
+        let lo = result & (Uint::from(2_u8).pow(64) - Uint::from(1_u8));
+        println!("{{{hi:#x}, {lo:#018x}}}, // {dec_exp:4}");
+    }
+}