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Diffstat (limited to 'absl/strings/escaping.cc')
| -rw-r--r-- | absl/strings/escaping.cc | 1093 |
1 files changed, 1093 insertions, 0 deletions
diff --git a/absl/strings/escaping.cc b/absl/strings/escaping.cc new file mode 100644 index 00000000..f1576057 --- /dev/null +++ b/absl/strings/escaping.cc @@ -0,0 +1,1093 @@ +// Copyright 2017 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 +// +// http://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/escaping.h" + +#include <cassert> +#include <cstdint> +#include <cstdio> +#include <cstring> +#include <limits> +#include <string> +#include <vector> + +#include "absl/base/internal/endian.h" +#include "absl/base/internal/raw_logging.h" +#include "absl/base/internal/unaligned_access.h" +#include "absl/base/macros.h" +#include "absl/base/port.h" +#include "absl/strings/internal/char_map.h" +#include "absl/strings/internal/resize_uninitialized.h" +#include "absl/strings/internal/utf8.h" +#include "absl/strings/str_join.h" +#include "absl/strings/string_view.h" + +namespace absl { +namespace { + +// Digit conversion. +constexpr char kHexChar[] = "0123456789abcdef"; + +constexpr char kHexTable[513] = + "000102030405060708090a0b0c0d0e0f" + "101112131415161718191a1b1c1d1e1f" + "202122232425262728292a2b2c2d2e2f" + "303132333435363738393a3b3c3d3e3f" + "404142434445464748494a4b4c4d4e4f" + "505152535455565758595a5b5c5d5e5f" + "606162636465666768696a6b6c6d6e6f" + "707172737475767778797a7b7c7d7e7f" + "808182838485868788898a8b8c8d8e8f" + "909192939495969798999a9b9c9d9e9f" + "a0a1a2a3a4a5a6a7a8a9aaabacadaeaf" + "b0b1b2b3b4b5b6b7b8b9babbbcbdbebf" + "c0c1c2c3c4c5c6c7c8c9cacbcccdcecf" + "d0d1d2d3d4d5d6d7d8d9dadbdcdddedf" + "e0e1e2e3e4e5e6e7e8e9eaebecedeeef" + "f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff"; + +// These are used for the leave_nulls_escaped argument to CUnescapeInternal(). +constexpr bool kUnescapeNulls = false; + +inline bool is_octal_digit(char c) { return ('0' <= c) && (c <= '7'); } + +inline int hex_digit_to_int(char c) { + static_assert('0' == 0x30 && 'A' == 0x41 && 'a' == 0x61, + "Character set must be ASCII."); + assert(absl::ascii_isxdigit(c)); + int x = static_cast<unsigned char>(c); + if (x > '9') { + x += 9; + } + return x & 0xf; +} + +// ---------------------------------------------------------------------- +// CUnescapeInternal() +// Implements both CUnescape() and CUnescapeForNullTerminatedString(). +// +// Unescapes C escape sequences and is the reverse of CEscape(). +// +// If 'source' is valid, stores the unescaped std::string and its size in +// 'dest' and 'dest_len' respectively, and returns true. Otherwise +// returns false and optionally stores the error description in +// 'error'. Set 'error' to nullptr to disable error reporting. +// +// 'dest' should point to a buffer that is at least as big as 'source'. +// 'source' and 'dest' may be the same. +// +// NOTE: any changes to this function must also be reflected in the older +// UnescapeCEscapeSequences(). +// ---------------------------------------------------------------------- +bool CUnescapeInternal(absl::string_view source, bool leave_nulls_escaped, + char* dest, ptrdiff_t* dest_len, std::string* error) { + char* d = dest; + const char* p = source.data(); + const char* end = source.end(); + const char* last_byte = end - 1; + + // Small optimization for case where source = dest and there's no escaping + while (p == d && p < end && *p != '\\') p++, d++; + + while (p < end) { + if (*p != '\\') { + *d++ = *p++; + } else { + if (++p > last_byte) { // skip past the '\\' + if (error) *error = "String cannot end with \\"; + return false; + } + switch (*p) { + case 'a': *d++ = '\a'; break; + case 'b': *d++ = '\b'; break; + case 'f': *d++ = '\f'; break; + case 'n': *d++ = '\n'; break; + case 'r': *d++ = '\r'; break; + case 't': *d++ = '\t'; break; + case 'v': *d++ = '\v'; break; + case '\\': *d++ = '\\'; break; + case '?': *d++ = '\?'; break; // \? Who knew? + case '\'': *d++ = '\''; break; + case '"': *d++ = '\"'; break; + case '0': + case '1': + case '2': + case '3': + case '4': + case '5': + case '6': + case '7': { + // octal digit: 1 to 3 digits + const char* octal_start = p; + unsigned int ch = *p - '0'; + if (p < last_byte && is_octal_digit(p[1])) ch = ch * 8 + *++p - '0'; + if (p < last_byte && is_octal_digit(p[1])) + ch = ch * 8 + *++p - '0'; // now points at last digit + if (ch > 0xff) { + if (error) { + *error = "Value of \\" + + std::string(octal_start, p + 1 - octal_start) + + " exceeds 0xff"; + } + return false; + } + if ((ch == 0) && leave_nulls_escaped) { + // Copy the escape sequence for the null character + const ptrdiff_t octal_size = p + 1 - octal_start; + *d++ = '\\'; + memcpy(d, octal_start, octal_size); + d += octal_size; + break; + } + *d++ = ch; + break; + } + case 'x': + case 'X': { + if (p >= last_byte) { + if (error) *error = "String cannot end with \\x"; + return false; + } else if (!absl::ascii_isxdigit(p[1])) { + if (error) *error = "\\x cannot be followed by a non-hex digit"; + return false; + } + unsigned int ch = 0; + const char* hex_start = p; + while (p < last_byte && absl::ascii_isxdigit(p[1])) + // Arbitrarily many hex digits + ch = (ch << 4) + hex_digit_to_int(*++p); + if (ch > 0xFF) { + if (error) { + *error = "Value of \\" + std::string(hex_start, p + 1 - hex_start) + + " exceeds 0xff"; + } + return false; + } + if ((ch == 0) && leave_nulls_escaped) { + // Copy the escape sequence for the null character + const ptrdiff_t hex_size = p + 1 - hex_start; + *d++ = '\\'; + memcpy(d, hex_start, hex_size); + d += hex_size; + break; + } + *d++ = ch; + break; + } + case 'u': { + // \uhhhh => convert 4 hex digits to UTF-8 + char32_t rune = 0; + const char* hex_start = p; + if (p + 4 >= end) { + if (error) { + *error = "\\u must be followed by 4 hex digits: \\" + + std::string(hex_start, p + 1 - hex_start); + } + return false; + } + for (int i = 0; i < 4; ++i) { + // Look one char ahead. + if (absl::ascii_isxdigit(p[1])) { + rune = (rune << 4) + hex_digit_to_int(*++p); // Advance p. + } else { + if (error) { + *error = "\\u must be followed by 4 hex digits: \\" + + std::string(hex_start, p + 1 - hex_start); + } + return false; + } + } + if ((rune == 0) && leave_nulls_escaped) { + // Copy the escape sequence for the null character + *d++ = '\\'; + memcpy(d, hex_start, 5); // u0000 + d += 5; + break; + } + d += strings_internal::EncodeUTF8Char(d, rune); + break; + } + case 'U': { + // \Uhhhhhhhh => convert 8 hex digits to UTF-8 + char32_t rune = 0; + const char* hex_start = p; + if (p + 8 >= end) { + if (error) { + *error = "\\U must be followed by 8 hex digits: \\" + + std::string(hex_start, p + 1 - hex_start); + } + return false; + } + for (int i = 0; i < 8; ++i) { + // Look one char ahead. + if (absl::ascii_isxdigit(p[1])) { + // Don't change rune until we're sure this + // is within the Unicode limit, but do advance p. + uint32_t newrune = (rune << 4) + hex_digit_to_int(*++p); + if (newrune > 0x10FFFF) { + if (error) { + *error = "Value of \\" + + std::string(hex_start, p + 1 - hex_start) + + " exceeds Unicode limit (0x10FFFF)"; + } + return false; + } else { + rune = newrune; + } + } else { + if (error) { + *error = "\\U must be followed by 8 hex digits: \\" + + std::string(hex_start, p + 1 - hex_start); + } + return false; + } + } + if ((rune == 0) && leave_nulls_escaped) { + // Copy the escape sequence for the null character + *d++ = '\\'; + memcpy(d, hex_start, 9); // U00000000 + d += 9; + break; + } + d += strings_internal::EncodeUTF8Char(d, rune); + break; + } + default: { + if (error) *error = std::string("Unknown escape sequence: \\") + *p; + return false; + } + } + p++; // read past letter we escaped + } + } + *dest_len = d - dest; + return true; +} + +// ---------------------------------------------------------------------- +// CUnescapeInternal() +// +// Same as above but uses a C++ std::string for output. 'source' and 'dest' +// may be the same. +// ---------------------------------------------------------------------- +bool CUnescapeInternal(absl::string_view source, bool leave_nulls_escaped, + std::string* dest, std::string* error) { + strings_internal::STLStringResizeUninitialized(dest, source.size()); + + ptrdiff_t dest_size; + if (!CUnescapeInternal(source, + leave_nulls_escaped, + const_cast<char*>(dest->data()), + &dest_size, + error)) { + return false; + } + dest->erase(dest_size); + return true; +} + +// ---------------------------------------------------------------------- +// CEscape() +// CHexEscape() +// Utf8SafeCEscape() +// Utf8SafeCHexEscape() +// Escapes 'src' using C-style escape sequences. This is useful for +// preparing query flags. The 'Hex' version uses hexadecimal rather than +// octal sequences. The 'Utf8Safe' version does not touch UTF-8 bytes. +// +// Escaped chars: \n, \r, \t, ", ', \, and !absl::ascii_isprint(). +// ---------------------------------------------------------------------- +std::string CEscapeInternal(absl::string_view src, bool use_hex, bool utf8_safe) { + std::string dest; + bool last_hex_escape = false; // true if last output char was \xNN. + + for (unsigned char c : src) { + bool is_hex_escape = false; + switch (c) { + case '\n': dest.append("\\" "n"); break; + case '\r': dest.append("\\" "r"); break; + case '\t': dest.append("\\" "t"); break; + case '\"': dest.append("\\" "\""); break; + case '\'': dest.append("\\" "'"); break; + case '\\': dest.append("\\" "\\"); break; + default: + // Note that if we emit \xNN and the src character after that is a hex + // digit then that digit must be escaped too to prevent it being + // interpreted as part of the character code by C. + if ((!utf8_safe || c < 0x80) && + (!absl::ascii_isprint(c) || + (last_hex_escape && absl::ascii_isxdigit(c)))) { + if (use_hex) { + dest.append("\\" "x"); + dest.push_back(kHexChar[c / 16]); + dest.push_back(kHexChar[c % 16]); + is_hex_escape = true; + } else { + dest.append("\\"); + dest.push_back(kHexChar[c / 64]); + dest.push_back(kHexChar[(c % 64) / 8]); + dest.push_back(kHexChar[c % 8]); + } + } else { + dest.push_back(c); + break; + } + } + last_hex_escape = is_hex_escape; + } + + return dest; +} + +// Calculates the length of the C-style escaped version of 'src'. +// Assumes that non-printable characters are escaped using octal sequences, and +// that UTF-8 bytes are not handled specially. +inline size_t CEscapedLength(absl::string_view src) { + /* clang-format off */ + constexpr char c_escaped_len[256] = { + 4, 4, 4, 4, 4, 4, 4, 4, 4, 2, 2, 4, 4, 2, 4, 4, // \t, \n, \r + 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, + 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, // ", ' + 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // '0'..'9' + 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 'A'..'O' + 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, // 'P'..'Z', '\' + 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 'a'..'o' + 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4, // 'p'..'z', DEL + 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, + 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, + 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, + 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, + 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, + 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, + 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, + 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, + }; + /* clang-format on */ + + size_t escaped_len = 0; + for (unsigned char c : src) escaped_len += c_escaped_len[c]; + return escaped_len; +} + +void CEscapeAndAppendInternal(absl::string_view src, std::string* dest) { + size_t escaped_len = CEscapedLength(src); + if (escaped_len == src.size()) { + dest->append(src.data(), src.size()); + return; + } + + size_t cur_dest_len = dest->size(); + strings_internal::STLStringResizeUninitialized(dest, + cur_dest_len + escaped_len); + char* append_ptr = &(*dest)[cur_dest_len]; + + for (unsigned char c : src) { + switch (c) { + case '\n': + *append_ptr++ = '\\'; + *append_ptr++ = 'n'; + break; + case '\r': + *append_ptr++ = '\\'; + *append_ptr++ = 'r'; + break; + case '\t': + *append_ptr++ = '\\'; + *append_ptr++ = 't'; + break; + case '\"': + *append_ptr++ = '\\'; + *append_ptr++ = '\"'; + break; + case '\'': + *append_ptr++ = '\\'; + *append_ptr++ = '\''; + break; + case '\\': + *append_ptr++ = '\\'; + *append_ptr++ = '\\'; + break; + default: + if (!absl::ascii_isprint(c)) { + *append_ptr++ = '\\'; + *append_ptr++ = '0' + c / 64; + *append_ptr++ = '0' + (c % 64) / 8; + *append_ptr++ = '0' + c % 8; + } else { + *append_ptr++ = c; + } + break; + } + } +} + +bool Base64UnescapeInternal(const char* src_param, size_t szsrc, char* dest, + size_t szdest, const signed char* unbase64, + size_t* len) { + static const char kPad64Equals = '='; + static const char kPad64Dot = '.'; + + size_t destidx = 0; + int decode = 0; + int state = 0; + unsigned int ch = 0; + unsigned int temp = 0; + + // If "char" is signed by default, using *src as an array index results in + // accessing negative array elements. Treat the input as a pointer to + // unsigned char to avoid this. + const unsigned char* src = reinterpret_cast<const unsigned char*>(src_param); + + // The GET_INPUT macro gets the next input character, skipping + // over any whitespace, and stopping when we reach the end of the + // std::string or when we read any non-data character. The arguments are + // an arbitrary identifier (used as a label for goto) and the number + // of data bytes that must remain in the input to avoid aborting the + // loop. +#define GET_INPUT(label, remain) \ + label: \ + --szsrc; \ + ch = *src++; \ + decode = unbase64[ch]; \ + if (decode < 0) { \ + if (absl::ascii_isspace(ch) && szsrc >= remain) goto label; \ + state = 4 - remain; \ + break; \ + } + + // if dest is null, we're just checking to see if it's legal input + // rather than producing output. (I suspect this could just be done + // with a regexp...). We duplicate the loop so this test can be + // outside it instead of in every iteration. + + if (dest) { + // This loop consumes 4 input bytes and produces 3 output bytes + // per iteration. We can't know at the start that there is enough + // data left in the std::string for a full iteration, so the loop may + // break out in the middle; if so 'state' will be set to the + // number of input bytes read. + + while (szsrc >= 4) { + // We'll start by optimistically assuming that the next four + // bytes of the std::string (src[0..3]) are four good data bytes + // (that is, no nulls, whitespace, padding chars, or illegal + // chars). We need to test src[0..2] for nulls individually + // before constructing temp to preserve the property that we + // never read past a null in the std::string (no matter how long + // szsrc claims the std::string is). + + if (!src[0] || !src[1] || !src[2] || + ((temp = ((unsigned(unbase64[src[0]]) << 18) | + (unsigned(unbase64[src[1]]) << 12) | + (unsigned(unbase64[src[2]]) << 6) | + (unsigned(unbase64[src[3]])))) & + 0x80000000)) { + // Iff any of those four characters was bad (null, illegal, + // whitespace, padding), then temp's high bit will be set + // (because unbase64[] is -1 for all bad characters). + // + // We'll back up and resort to the slower decoder, which knows + // how to handle those cases. + + GET_INPUT(first, 4); + temp = decode; + GET_INPUT(second, 3); + temp = (temp << 6) | decode; + GET_INPUT(third, 2); + temp = (temp << 6) | decode; + GET_INPUT(fourth, 1); + temp = (temp << 6) | decode; + } else { + // We really did have four good data bytes, so advance four + // characters in the std::string. + + szsrc -= 4; + src += 4; + } + + // temp has 24 bits of input, so write that out as three bytes. + + if (destidx + 3 > szdest) return false; + dest[destidx + 2] = temp; + temp >>= 8; + dest[destidx + 1] = temp; + temp >>= 8; + dest[destidx] = temp; + destidx += 3; + } + } else { + while (szsrc >= 4) { + if (!src[0] || !src[1] || !src[2] || + ((temp = ((unsigned(unbase64[src[0]]) << 18) | + (unsigned(unbase64[src[1]]) << 12) | + (unsigned(unbase64[src[2]]) << 6) | + (unsigned(unbase64[src[3]])))) & + 0x80000000)) { + GET_INPUT(first_no_dest, 4); + GET_INPUT(second_no_dest, 3); + GET_INPUT(third_no_dest, 2); + GET_INPUT(fourth_no_dest, 1); + } else { + szsrc -= 4; + src += 4; + } + destidx += 3; + } + } + +#undef GET_INPUT + + // if the loop terminated because we read a bad character, return + // now. + if (decode < 0 && ch != kPad64Equals && ch != kPad64Dot && + !absl::ascii_isspace(ch)) + return false; + + if (ch == kPad64Equals || ch == kPad64Dot) { + // if we stopped by hitting an '=' or '.', un-read that character -- we'll + // look at it again when we count to check for the proper number of + // equals signs at the end. + ++szsrc; + --src; + } else { + // This loop consumes 1 input byte per iteration. It's used to + // clean up the 0-3 input bytes remaining when the first, faster + // loop finishes. 'temp' contains the data from 'state' input + // characters read by the first loop. + while (szsrc > 0) { + --szsrc; + ch = *src++; + decode = unbase64[ch]; + if (decode < 0) { + if (absl::ascii_isspace(ch)) { + continue; + } else if (ch == kPad64Equals || ch == kPad64Dot) { + // back up one character; we'll read it again when we check + // for the correct number of pad characters at the end. + ++szsrc; + --src; + break; + } else { + return false; + } + } + + // Each input character gives us six bits of output. + temp = (temp << 6) | decode; + ++state; + if (state == 4) { + // If we've accumulated 24 bits of output, write that out as + // three bytes. + if (dest) { + if (destidx + 3 > szdest) return false; + dest[destidx + 2] = temp; + temp >>= 8; + dest[destidx + 1] = temp; + temp >>= 8; + dest[destidx] = temp; + } + destidx += 3; + state = 0; + temp = 0; + } + } + } + + // Process the leftover data contained in 'temp' at the end of the input. + int expected_equals = 0; + switch (state) { + case 0: + // Nothing left over; output is a multiple of 3 bytes. + break; + + case 1: + // Bad input; we have 6 bits left over. + return false; + + case 2: + // Produce one more output byte from the 12 input bits we have left. + if (dest) { + if (destidx + 1 > szdest) return false; + temp >>= 4; + dest[destidx] = temp; + } + ++destidx; + expected_equals = 2; + break; + + case 3: + // Produce two more output bytes from the 18 input bits we have left. + if (dest) { + if (destidx + 2 > szdest) return false; + temp >>= 2; + dest[destidx + 1] = temp; + temp >>= 8; + dest[destidx] = temp; + } + destidx += 2; + expected_equals = 1; + break; + + default: + // state should have no other values at this point. + ABSL_RAW_LOG(FATAL, "This can't happen; base64 decoder state = %d", + state); + } + + // The remainder of the std::string should be all whitespace, mixed with + // exactly 0 equals signs, or exactly 'expected_equals' equals + // signs. (Always accepting 0 equals signs is an Abseil extension + // not covered in the RFC, as is accepting dot as the pad character.) + + int equals = 0; + while (szsrc > 0) { + if (*src == kPad64Equals || *src == kPad64Dot) + ++equals; + else if (!absl::ascii_isspace(*src)) + return false; + --szsrc; + ++src; + } + + const bool ok = (equals == 0 || equals == expected_equals); + if (ok) *len = destidx; + return ok; +} + +// The arrays below were generated by the following code +// #include <sys/time.h> +// #include <stdlib.h> +// #include <std::string.h> +// main() +// { +// static const char Base64[] = +// "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; +// char* pos; +// int idx, i, j; +// printf(" "); +// for (i = 0; i < 255; i += 8) { +// for (j = i; j < i + 8; j++) { +// pos = strchr(Base64, j); +// if ((pos == nullptr) || (j == 0)) +// idx = -1; +// else +// idx = pos - Base64; +// if (idx == -1) +// printf(" %2d, ", idx); +// else +// printf(" %2d/*%c*/,", idx, j); +// } +// printf("\n "); +// } +// } +// +// where the value of "Base64[]" was replaced by one of the base-64 conversion +// tables from the functions below. +/* clang-format off */ +constexpr signed char kUnBase64[] = { + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, 62/*+*/, -1, -1, -1, 63/*/ */, + 52/*0*/, 53/*1*/, 54/*2*/, 55/*3*/, 56/*4*/, 57/*5*/, 58/*6*/, 59/*7*/, + 60/*8*/, 61/*9*/, -1, -1, -1, -1, -1, -1, + -1, 0/*A*/, 1/*B*/, 2/*C*/, 3/*D*/, 4/*E*/, 5/*F*/, 6/*G*/, + 07/*H*/, 8/*I*/, 9/*J*/, 10/*K*/, 11/*L*/, 12/*M*/, 13/*N*/, 14/*O*/, + 15/*P*/, 16/*Q*/, 17/*R*/, 18/*S*/, 19/*T*/, 20/*U*/, 21/*V*/, 22/*W*/, + 23/*X*/, 24/*Y*/, 25/*Z*/, -1, -1, -1, -1, -1, + -1, 26/*a*/, 27/*b*/, 28/*c*/, 29/*d*/, 30/*e*/, 31/*f*/, 32/*g*/, + 33/*h*/, 34/*i*/, 35/*j*/, 36/*k*/, 37/*l*/, 38/*m*/, 39/*n*/, 40/*o*/, + 41/*p*/, 42/*q*/, 43/*r*/, 44/*s*/, 45/*t*/, 46/*u*/, 47/*v*/, 48/*w*/, + 49/*x*/, 50/*y*/, 51/*z*/, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1 +}; + +constexpr signed char kUnWebSafeBase64[] = { + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, 62/*-*/, -1, -1, + 52/*0*/, 53/*1*/, 54/*2*/, 55/*3*/, 56/*4*/, 57/*5*/, 58/*6*/, 59/*7*/, + 60/*8*/, 61/*9*/, -1, -1, -1, -1, -1, -1, + -1, 0/*A*/, 1/*B*/, 2/*C*/, 3/*D*/, 4/*E*/, 5/*F*/, 6/*G*/, + 07/*H*/, 8/*I*/, 9/*J*/, 10/*K*/, 11/*L*/, 12/*M*/, 13/*N*/, 14/*O*/, + 15/*P*/, 16/*Q*/, 17/*R*/, 18/*S*/, 19/*T*/, 20/*U*/, 21/*V*/, 22/*W*/, + 23/*X*/, 24/*Y*/, 25/*Z*/, -1, -1, -1, -1, 63/*_*/, + -1, 26/*a*/, 27/*b*/, 28/*c*/, 29/*d*/, 30/*e*/, 31/*f*/, 32/*g*/, + 33/*h*/, 34/*i*/, 35/*j*/, 36/*k*/, 37/*l*/, 38/*m*/, 39/*n*/, 40/*o*/, + 41/*p*/, 42/*q*/, 43/*r*/, 44/*s*/, 45/*t*/, 46/*u*/, 47/*v*/, 48/*w*/, + 49/*x*/, 50/*y*/, 51/*z*/, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1 +}; +/* clang-format on */ + +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 http://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 http://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 http://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 http://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) { // as long as 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); +} + +constexpr char kBase64Chars[] = + "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; + +constexpr char kWebSafeBase64Chars[] = + "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"; + +void Base64EscapeInternal(const unsigned char* src, size_t szsrc, std::string* dest, + bool do_padding, const char* base64_chars) { + const size_t calc_escaped_size = + CalculateBase64EscapedLenInternal(szsrc, do_padding); + strings_internal::STLStringResizeUninitialized(dest, calc_escaped_size); + + const size_t escaped_len = Base64EscapeInternal( + src, szsrc, &(*dest)[0], dest->size(), base64_chars, do_padding); + assert(calc_escaped_size == escaped_len); + dest->erase(escaped_len); +} + +bool Base64UnescapeInternal(const char* src, size_t slen, std::string* dest, + const signed char* unbase64) { + // Determine the size of the output std::string. Base64 encodes every 3 bytes into + // 4 characters. any leftover chars are added directly for good measure. + // This is documented in the base64 RFC: http://tools.ietf.org/html/rfc3548 + const size_t dest_len = 3 * (slen / 4) + (slen % 4); + + strings_internal::STLStringResizeUninitialized(dest, dest_len); + + // We are getting the destination buffer by getting the beginning of the + // std::string and converting it into a char *. + size_t len; + const bool ok = + Base64UnescapeInternal(src, slen, &(*dest)[0], dest_len, unbase64, &len); + if (!ok) { + dest->clear(); + return false; + } + + // could be shorter if there was padding + assert(len <= dest_len); + dest->erase(len); + + return true; +} + +/* clang-format off */ +constexpr char kHexValue[256] = { + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 0, 0, 0, 0, // '0'..'9' + 0, 10, 11, 12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 'A'..'F' + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 10, 11, 12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 'a'..'f' + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 +}; +/* clang-format on */ + +// This is a templated function so that T can be either a char* +// or a std::string. This works because we use the [] operator to access +// individual characters at a time. +template <typename T> +void HexStringToBytesInternal(const char* from, T to, ptrdiff_t num) { + for (int i = 0; i < num; i++) { + to[i] = (kHexValue[from[i * 2] & 0xFF] << 4) + + (kHexValue[from[i * 2 + 1] & 0xFF]); + } +} + +// This is a templated function so that T can be either a char* or a std::string. +template <typename T> +void BytesToHexStringInternal(const unsigned char* src, T dest, ptrdiff_t num) { + auto dest_ptr = &dest[0]; + for (auto src_ptr = src; src_ptr != (src + num); ++src_ptr, dest_ptr += 2) { + const char* hex_p = &kHexTable[*src_ptr * 2]; + std::copy(hex_p, hex_p + 2, dest_ptr); + } +} + +} // namespace + +// ---------------------------------------------------------------------- +// CUnescape() +// +// See CUnescapeInternal() for implementation details. +// ---------------------------------------------------------------------- +bool CUnescape(absl::string_view source, std::string* dest, std::string* error) { + return CUnescapeInternal(source, kUnescapeNulls, dest, error); +} + +std::string CEscape(absl::string_view src) { + std::string dest; + CEscapeAndAppendInternal(src, &dest); + return dest; +} + +std::string CHexEscape(absl::string_view src) { + return CEscapeInternal(src, true, false); +} + +std::string Utf8SafeCEscape(absl::string_view src) { + return CEscapeInternal(src, false, true); +} + +std::string Utf8SafeCHexEscape(absl::string_view src) { + return CEscapeInternal(src, true, true); +} + +// ---------------------------------------------------------------------- +// ptrdiff_t Base64Unescape() - base64 decoder +// ptrdiff_t Base64Escape() - base64 encoder +// ptrdiff_t WebSafeBase64Unescape() - Google's variation of base64 decoder +// ptrdiff_t WebSafeBase64Escape() - Google's variation of base64 encoder +// +// Check out +// http://tools.ietf.org/html/rfc2045 for formal description, but what we +// care about is that... +// Take the encoded stuff in groups of 4 characters and turn each +// character into a code 0 to 63 thus: +// A-Z map to 0 to 25 +// a-z map to 26 to 51 +// 0-9 map to 52 to 61 +// +(- for WebSafe) maps to 62 +// /(_ for WebSafe) maps to 63 +// There will be four numbers, all less than 64 which can be represented +// by a 6 digit binary number (aaaaaa, bbbbbb, cccccc, dddddd respectively). +// Arrange the 6 digit binary numbers into three bytes as such: +// aaaaaabb bbbbcccc ccdddddd +// Equals signs (one or two) are used at the end of the encoded block to +// indicate that the text was not an integer multiple of three bytes long. +// ---------------------------------------------------------------------- + +bool Base64Unescape(absl::string_view src, std::string* dest) { + return Base64UnescapeInternal(src.data(), src.size(), dest, kUnBase64); +} + +bool WebSafeBase64Unescape(absl::string_view src, std::string* dest) { + return Base64UnescapeInternal(src.data(), src.size(), dest, kUnWebSafeBase64); +} + +void Base64Escape(absl::string_view src, std::string* dest) { + Base64EscapeInternal(reinterpret_cast<const unsigned char*>(src.data()), + src.size(), dest, true, kBase64Chars); +} + +void WebSafeBase64Escape(absl::string_view src, std::string* dest) { + Base64EscapeInternal(reinterpret_cast<const unsigned char*>(src.data()), + src.size(), dest, false, kWebSafeBase64Chars); +} + +std::string HexStringToBytes(absl::string_view from) { + std::string result; + const auto num = from.size() / 2; + strings_internal::STLStringResizeUninitialized(&result, num); + absl::HexStringToBytesInternal<std::string&>(from.data(), result, num); + return result; +} + +std::string BytesToHexString(absl::string_view from) { + std::string result; + strings_internal::STLStringResizeUninitialized(&result, 2 * from.size()); + absl::BytesToHexStringInternal<std::string&>( + reinterpret_cast<const unsigned char*>(from.data()), result, from.size()); + return result; +} + +} // namespace absl |