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android / platform / external / dynamic_depth / refs/tags/android-11.0.0_r28 / . / internal / strings / escaping.cc
blob: 7386e4a7b92e3063e7fcad0e040eb0f48f2d8629 [file] [log] [blame]
#include "strings/escaping.h"
#include <cassert>
#include "android-base/logging.h"
#include "strings/ascii_ctype.h"
namespace dynamic_depth {
// ----------------------------------------------------------------------
// 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 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
// 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 (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 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 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 string (no matter how long
// szsrc claims the 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 string.
szsrc -= 4;
src += 4;
decode = -1;
ch = '\0';
}
// 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;
decode = -1;
ch = '\0';
}
destidx += 3;
}
}
#undef GET_INPUT
// if the loop terminated because we read a bad character, return
// now.
if (decode < 0 && ch != '\0' && ch != kPad64Equals && ch != kPad64Dot &&
!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 (ascii_isspace(ch)) {
continue;
} else if (ch == '\0') {
break;
} 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.
LOG(FATAL) << "This can't happen; base64 decoder state = " << state;
}
// The remainder of the string should be all whitespace, mixed with
// exactly 0 equals signs, or exactly 'expected_equals' equals
// signs. (Always accepting 0 equals signs is a google extension
// not covered in the RFC, as is accepting dot as the pad character.)
int equals = 0;
while (szsrc > 0 && *src) {
if (*src == kPad64Equals || *src == kPad64Dot)
++equals;
else if (!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 <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 == NULL) || (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.
static const 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};
static const 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};
static bool Base64UnescapeInternal(const char* src, size_t slen, string* dest,
const signed char* unbase64) {
// Determine the size of the output 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);
dest->resize(dest_len);
// We are getting the destination buffer by getting the beginning of the
// string and converting it into a char *.
size_t len;
const bool ok =
Base64UnescapeInternal(src, slen, dest->empty() ? NULL : &*dest->begin(),
dest_len, unbase64, &len);
if (!ok) {
dest->clear();
return false;
}
// could be shorter if there was padding
DCHECK_LE(len, dest_len);
dest->erase(len);
return true;
}
bool Base64Unescape(const string& src, string* dest) {
return Base64UnescapeInternal(src.data(), src.size(), dest, kUnBase64);
}
bool WebSafeBase64Unescape(const string& src, string* dest) {
return Base64UnescapeInternal(src.data(), src.size(), dest, kUnWebSafeBase64);
}
// Base64Escape
//
// NOTE: We have to use an unsigned type for src because code built
// in the the /google tree treats characters as signed unless
// otherwised specified.
int Base64EscapeInternal(const unsigned char* src, int szsrc, char* dest,
int szdest, const char* base64, bool do_padding) {
static const char kPad64 = '=';
if (szsrc <= 0) return 0;
char* cur_dest = dest;
const unsigned char* cur_src = src;
// Three bytes of data encodes to four characters of cyphertext.
// So we can pump through three-byte chunks atomically.
while (szsrc > 2) { /* keep going until we have less than 24 bits */
if ((szdest -= 4) < 0) return 0;
cur_dest[0] = base64[cur_src[0] >> 2];
cur_dest[1] = base64[((cur_src[0] & 0x03) << 4) + (cur_src[1] >> 4)];
cur_dest[2] = base64[((cur_src[1] & 0x0f) << 2) + (cur_src[2] >> 6)];
cur_dest[3] = base64[cur_src[2] & 0x3f];
cur_dest += 4;
cur_src += 3;
szsrc -= 3;
}
/* now deal with the tail (<=2 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) < 0) return 0;
cur_dest[0] = base64[cur_src[0] >> 2];
cur_dest[1] = base64[(cur_src[0] & 0x03) << 4];
cur_dest += 2;
if (do_padding) {
if ((szdest -= 2) < 0) return 0;
cur_dest[0] = kPad64;
cur_dest[1] = kPad64;
cur_dest += 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) < 0) return 0;
cur_dest[0] = base64[cur_src[0] >> 2];
cur_dest[1] = base64[((cur_src[0] & 0x03) << 4) + (cur_src[1] >> 4)];
cur_dest[2] = base64[(cur_src[1] & 0x0f) << 2];
cur_dest += 3;
if (do_padding) {
if ((szdest -= 1) < 0) return 0;
cur_dest[0] = kPad64;
cur_dest += 1;
}
break;
default:
// Should not be reached: blocks of 3 bytes are handled
// in the while loop before this switch statement.
CHECK(false) << "Logic problem? szsrc = " << szsrc;
break;
}
return (cur_dest - dest);
}
static const char kBase64Chars[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
// Digit conversion.
static const char kHexTable[513] =
"000102030405060708090a0b0c0d0e0f"
"101112131415161718191a1b1c1d1e1f"
"202122232425262728292a2b2c2d2e2f"
"303132333435363738393a3b3c3d3e3f"
"404142434445464748494a4b4c4d4e4f"
"505152535455565758595a5b5c5d5e5f"
"606162636465666768696a6b6c6d6e6f"
"707172737475767778797a7b7c7d7e7f"
"808182838485868788898a8b8c8d8e8f"
"909192939495969798999a9b9c9d9e9f"
"a0a1a2a3a4a5a6a7a8a9aaabacadaeaf"
"b0b1b2b3b4b5b6b7b8b9babbbcbdbebf"
"c0c1c2c3c4c5c6c7c8c9cacbcccdcecf"
"d0d1d2d3d4d5d6d7d8d9dadbdcdddedf"
"e0e1e2e3e4e5e6e7e8e9eaebecedeeef"
"f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff";
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;
}
void Base64EscapeInternal(const unsigned char* src, size_t szsrc, string* dest,
bool do_padding, const char* base64_chars) {
const size_t calc_escaped_size =
CalculateBase64EscapedLenInternal(szsrc, do_padding);
dest->resize(calc_escaped_size);
const int escaped_len = Base64EscapeInternal(
src, static_cast<int>(szsrc), dest->empty() ? NULL : &*dest->begin(),
static_cast<int>(dest->size()), base64_chars, do_padding);
DCHECK_EQ(calc_escaped_size, escaped_len);
dest->erase(escaped_len);
}
void Base64Escape(const unsigned char* src, ptrdiff_t szsrc, string* dest,
bool do_padding) {
if (szsrc < 0) return;
Base64EscapeInternal(src, szsrc, dest, do_padding, kBase64Chars);
}
// This is a templated function so that T can be either a char* or a string.
template <typename T>
static void b2a_hex_t(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);
}
}
string b2a_hex(const char* b, ptrdiff_t len) {
string result;
result.resize(len << 1);
b2a_hex_t<string&>(reinterpret_cast<const unsigned char*>(b), result, len);
return result;
}
} // namespace dynamic_depth