From 7293b32025e2b14fcb2d2db54c472a3a9fa12488 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Mon, 14 Mar 2022 12:08:06 +0100
Subject: [PATCH] util/HexFormat: faster implementation without snprintf()
---
src/util/HexFormat.cxx | 43 -----------------------
src/util/HexFormat.hxx | 79 ++++++++++++++++++++++++++++++++++--------
src/util/meson.build | 1 -
3 files changed, 65 insertions(+), 58 deletions(-)
delete mode 100644 src/util/HexFormat.cxx
diff --git a/src/util/HexFormat.cxx b/src/util/HexFormat.cxx
deleted file mode 100644
index 1a048eb23..000000000
--- a/src/util/HexFormat.cxx
+++ /dev/null
@@ -1,43 +0,0 @@
-/*
- * Copyright (C) 2018 Max Kellermann <max.kellermann@gmail.com>
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * - Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * - Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the
- * distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
- * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
- * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
- * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
- * OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include "HexFormat.hxx"
-
-#include <stdio.h>
-
-char *
-HexFormat(char *dest, ConstBuffer<uint8_t> src) noexcept
-{
- for (auto i : src) {
- sprintf(dest, "%02x", i);
- dest += 2;
- }
-
- return dest;
-}
diff --git a/src/util/HexFormat.hxx b/src/util/HexFormat.hxx
index 93f5127bd..cea55135e 100644
--- a/src/util/HexFormat.hxx
+++ b/src/util/HexFormat.hxx
@@ -1,5 +1,8 @@
/*
- * Copyright (C) 2018 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2007-2022 CM4all GmbH
+ * All rights reserved.
+ *
+ * author: Max Kellermann <mk@cm4all.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
@@ -27,8 +30,7 @@
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
-#ifndef HEX_FORMAT_HXX
-#define HEX_FORMAT_HXX
+#pragma once
#include "ConstBuffer.hxx"
#include "StringBuffer.hxx"
@@ -36,16 +38,67 @@
#include <cstddef>
#include <cstdint>
+constexpr char hex_digits[] = "0123456789abcdef";
+
+[[gnu::always_inline]]
+static constexpr char *
+HexFormatUint8Fixed(char dest[2], uint8_t number) noexcept
+{
+ dest[0] = hex_digits[(number >> 4) & 0xf];
+ dest[1] = hex_digits[number & 0xf];
+ return dest + 2;
+}
+
+[[gnu::always_inline]]
+static constexpr char *
+HexFormatUint16Fixed(char dest[4], uint16_t number) noexcept
+{
+ dest[0] = hex_digits[(number >> 12) & 0xf];
+ dest[1] = hex_digits[(number >> 8) & 0xf];
+ dest[2] = hex_digits[(number >> 4) & 0xf];
+ dest[3] = hex_digits[number & 0xf];
+ return dest + 4;
+}
+
+[[gnu::always_inline]]
+static constexpr char *
+HexFormatUint32Fixed(char dest[8], uint32_t number) noexcept
+{
+ dest[0] = hex_digits[(number >> 28) & 0xf];
+ dest[1] = hex_digits[(number >> 24) & 0xf];
+ dest[2] = hex_digits[(number >> 20) & 0xf];
+ dest[3] = hex_digits[(number >> 16) & 0xf];
+ dest[4] = hex_digits[(number >> 12) & 0xf];
+ dest[5] = hex_digits[(number >> 8) & 0xf];
+ dest[6] = hex_digits[(number >> 4) & 0xf];
+ dest[7] = hex_digits[number & 0xf];
+ return dest + 8;
+}
+
+[[gnu::always_inline]]
+static constexpr char *
+HexFormatUint64Fixed(char dest[16], uint64_t number) noexcept
+{
+ dest = HexFormatUint32Fixed(dest, number >> 32);
+ dest = HexFormatUint32Fixed(dest, number);
+ return dest;
+}
+
/**
- * Format the given byte sequence into a null-terminated hexadecimal
- * string.
+ * Format the given input buffer of bytes to hex. The caller ensures
+ * that the output buffer is at least twice as large as the input.
+ * Does not null-terminate the output buffer.
*
- * @param dest the destination buffer; must be large enough to hold
- * all hex digits plus the null terminator
- * @return a pointer to the generated null terminator
+ * @return a pointer to one after the last written character
*/
-char *
-HexFormat(char *dest, ConstBuffer<uint8_t> src) noexcept;
+constexpr char *
+HexFormat(char *output, ConstBuffer<uint8_t> input) noexcept
+{
+ for (const auto &i : input)
+ output = HexFormatUint8Fixed(output, i);
+
+ return output;
+}
/**
* Like HexFormat(), but return a #StringBuffer with exactly the
@@ -53,12 +106,10 @@ HexFormat(char *dest, ConstBuffer<uint8_t> src) noexcept;
*/
template<size_t size>
[[gnu::pure]]
-auto
+constexpr auto
HexFormatBuffer(const uint8_t *src) noexcept
{
StringBuffer<size * 2 + 1> dest;
- HexFormat(dest.data(), {src, size});
+ *HexFormat(dest.data(), {src, size}) = 0;
return dest;
}
-
-#endif
diff --git a/src/util/meson.build b/src/util/meson.build
index 2a13058e7..9c5d94e81 100644
--- a/src/util/meson.build
+++ b/src/util/meson.build
@@ -2,7 +2,6 @@ util = static_library(
'util',
'Exception.cxx',
'UTF8.cxx',
- 'HexFormat.cxx',
'MimeType.cxx',
'NumberParser.cxx',
'StringView.cxx',