From b3aaac8a37c467a1125c794196caa90d0957bdc3 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Thu, 9 Jan 2020 09:58:48 -0800 Subject: Export of internal Abseil changes -- 9beb68204986a015c9cb065b9fae4f9a8879a788 by Abseil Team : Move Base64EscapeInternal and CalculateBase64EscapedLenInternal to an internal header. PiperOrigin-RevId: 288917378 -- 90acfbe03b3f9f6de3ffa49c39343dfaa2c5d38c by Greg Falcon : Update macos CI script to support the ALTERNATE_OPTIONS environment variable. PiperOrigin-RevId: 288913564 -- f1572e870678cdcda6b48cb39780d1ad984e4c1b by Derek Mauro : Makes absl::NullSafeStringView constexpr Fixes https://github.com/abseil/abseil-cpp/issues/583 PiperOrigin-RevId: 288906940 -- d28a8471e32c10caa64bfffe6d6d4d0a8d144013 by Abseil Team : absl::GetFlag is lock free for small trivially copyable types. PiperOrigin-RevId: 288768172 -- 2643b8ed1a1dc836b38ab9e46538a1af129ffd67 by Gennadiy Rozental : Eliminate call to callback from flag initialization. We do not need to have this invocation inside FlagImpl::Init since SetCallback performs invocation anyways. Calling InitCallback from inside of Init complicates separation of value initialization from data guard initialization, which is about to happen. PiperOrigin-RevId: 288732526 -- 22caa880b7a4cb6da34e16a2e064a473c99e880b by Abseil Team : Fix the documentation on how to create a null string_view. PiperOrigin-RevId: 288727968 -- 10727c5cadc561837141176f4c9b9717cec9233a by Greg Falcon : Change CI scripts for gcc to use the ALTERNATE_OPTIONS file as well. PiperOrigin-RevId: 288718855 -- 5d1e2dd6c7fb12af8aa4337a0f61872f5f0c5992 by Greg Falcon : Add an option for using inline namespaces in Abseil. PiperOrigin-RevId: 288614491 GitOrigin-RevId: 9beb68204986a015c9cb065b9fae4f9a8879a788 Change-Id: If9acd46301e3df8cb231b4c16f7ed651bf4fb3c3 --- absl/strings/internal/escaping.cc | 180 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 180 insertions(+) create mode 100644 absl/strings/internal/escaping.cc (limited to 'absl/strings/internal/escaping.cc') diff --git a/absl/strings/internal/escaping.cc b/absl/strings/internal/escaping.cc new file mode 100644 index 0000000..c527128 --- /dev/null +++ b/absl/strings/internal/escaping.cc @@ -0,0 +1,180 @@ +// Copyright 2020 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/strings/internal/escaping.h" + +#include "absl/base/internal/endian.h" +#include "absl/base/internal/raw_logging.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace strings_internal { + +const char kBase64Chars[] = + "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; + +size_t CalculateBase64EscapedLenInternal(size_t input_len, bool do_padding) { + // Base64 encodes three bytes of input at a time. If the input is not + // divisible by three, we pad as appropriate. + // + // (from https://tools.ietf.org/html/rfc3548) + // Special processing is performed if fewer than 24 bits are available + // at the end of the data being encoded. A full encoding quantum is + // always completed at the end of a quantity. When fewer than 24 input + // bits are available in an input group, zero bits are added (on the + // right) to form an integral number of 6-bit groups. Padding at the + // end of the data is performed using the '=' character. Since all base + // 64 input is an integral number of octets, only the following cases + // can arise: + + // Base64 encodes each three bytes of input into four bytes of output. + size_t len = (input_len / 3) * 4; + + if (input_len % 3 == 0) { + // (from https://tools.ietf.org/html/rfc3548) + // (1) the final quantum of encoding input is an integral multiple of 24 + // bits; here, the final unit of encoded output will be an integral + // multiple of 4 characters with no "=" padding, + } else if (input_len % 3 == 1) { + // (from https://tools.ietf.org/html/rfc3548) + // (2) the final quantum of encoding input is exactly 8 bits; here, the + // final unit of encoded output will be two characters followed by two + // "=" padding characters, or + len += 2; + if (do_padding) { + len += 2; + } + } else { // (input_len % 3 == 2) + // (from https://tools.ietf.org/html/rfc3548) + // (3) the final quantum of encoding input is exactly 16 bits; here, the + // final unit of encoded output will be three characters followed by one + // "=" padding character. + len += 3; + if (do_padding) { + len += 1; + } + } + + assert(len >= input_len); // make sure we didn't overflow + return len; +} + +size_t Base64EscapeInternal(const unsigned char* src, size_t szsrc, char* dest, + size_t szdest, const char* base64, + bool do_padding) { + static const char kPad64 = '='; + + if (szsrc * 4 > szdest * 3) return 0; + + char* cur_dest = dest; + const unsigned char* cur_src = src; + + char* const limit_dest = dest + szdest; + const unsigned char* const limit_src = src + szsrc; + + // Three bytes of data encodes to four characters of cyphertext. + // So we can pump through three-byte chunks atomically. + if (szsrc >= 3) { // "limit_src - 3" is UB if szsrc < 3. + while (cur_src < limit_src - 3) { // While we have >= 32 bits. + uint32_t in = absl::big_endian::Load32(cur_src) >> 8; + + cur_dest[0] = base64[in >> 18]; + in &= 0x3FFFF; + cur_dest[1] = base64[in >> 12]; + in &= 0xFFF; + cur_dest[2] = base64[in >> 6]; + in &= 0x3F; + cur_dest[3] = base64[in]; + + cur_dest += 4; + cur_src += 3; + } + } + // To save time, we didn't update szdest or szsrc in the loop. So do it now. + szdest = limit_dest - cur_dest; + szsrc = limit_src - cur_src; + + /* now deal with the tail (<=3 bytes) */ + switch (szsrc) { + case 0: + // Nothing left; nothing more to do. + break; + case 1: { + // One byte left: this encodes to two characters, and (optionally) + // two pad characters to round out the four-character cypherblock. + if (szdest < 2) return 0; + uint32_t in = cur_src[0]; + cur_dest[0] = base64[in >> 2]; + in &= 0x3; + cur_dest[1] = base64[in << 4]; + cur_dest += 2; + szdest -= 2; + if (do_padding) { + if (szdest < 2) return 0; + cur_dest[0] = kPad64; + cur_dest[1] = kPad64; + cur_dest += 2; + szdest -= 2; + } + break; + } + case 2: { + // Two bytes left: this encodes to three characters, and (optionally) + // one pad character to round out the four-character cypherblock. + if (szdest < 3) return 0; + uint32_t in = absl::big_endian::Load16(cur_src); + cur_dest[0] = base64[in >> 10]; + in &= 0x3FF; + cur_dest[1] = base64[in >> 4]; + in &= 0x00F; + cur_dest[2] = base64[in << 2]; + cur_dest += 3; + szdest -= 3; + if (do_padding) { + if (szdest < 1) return 0; + cur_dest[0] = kPad64; + cur_dest += 1; + szdest -= 1; + } + break; + } + case 3: { + // Three bytes left: same as in the big loop above. We can't do this in + // the loop because the loop above always reads 4 bytes, and the fourth + // byte is past the end of the input. + if (szdest < 4) return 0; + uint32_t in = (cur_src[0] << 16) + absl::big_endian::Load16(cur_src + 1); + cur_dest[0] = base64[in >> 18]; + in &= 0x3FFFF; + cur_dest[1] = base64[in >> 12]; + in &= 0xFFF; + cur_dest[2] = base64[in >> 6]; + in &= 0x3F; + cur_dest[3] = base64[in]; + cur_dest += 4; + szdest -= 4; + break; + } + default: + // Should not be reached: blocks of 4 bytes are handled + // in the while loop before this switch statement. + ABSL_RAW_LOG(FATAL, "Logic problem? szsrc = %zu", szsrc); + break; + } + return (cur_dest - dest); +} + +} // namespace strings_internal +ABSL_NAMESPACE_END +} // namespace absl -- cgit v1.2.3