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/*-------------------------------------------------------------------------
*
* base64.c
* Encoding and decoding routines for base64 without whitespace.
*
* Copyright (c) 2001-2023, PostgreSQL Global Development Group
*
*
* IDENTIFICATION
* src/common/base64.c
*
*-------------------------------------------------------------------------
*/
#ifndef FRONTEND
#include "postgres.h"
#else
#include "postgres_fe.h"
#endif
#include "common/base64.h"
/*
* BASE64
*/
static const char _base64[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const int8 b64lookup[128] = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -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, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
};
/*
* pg_b64_encode
*
* Encode into base64 the given string. Returns the length of the encoded
* string, and -1 in the event of an error with the result buffer zeroed
* for safety.
*/
int
pg_b64_encode(const char *src, int len, char *dst, int dstlen)
{
char *p;
const char *s,
*end = src + len;
int pos = 2;
uint32 buf = 0;
s = src;
p = dst;
while (s < end)
{
buf |= (unsigned char) *s << (pos << 3);
pos--;
s++;
/* write it out */
if (pos < 0)
{
/*
* Leave if there is an overflow in the area allocated for the
* encoded string.
*/
if ((p - dst + 4) > dstlen)
goto error;
*p++ = _base64[(buf >> 18) & 0x3f];
*p++ = _base64[(buf >> 12) & 0x3f];
*p++ = _base64[(buf >> 6) & 0x3f];
*p++ = _base64[buf & 0x3f];
pos = 2;
buf = 0;
}
}
if (pos != 2)
{
/*
* Leave if there is an overflow in the area allocated for the encoded
* string.
*/
if ((p - dst + 4) > dstlen)
goto error;
*p++ = _base64[(buf >> 18) & 0x3f];
*p++ = _base64[(buf >> 12) & 0x3f];
*p++ = (pos == 0) ? _base64[(buf >> 6) & 0x3f] : '=';
*p++ = '=';
}
Assert((p - dst) <= dstlen);
return p - dst;
error:
memset(dst, 0, dstlen);
return -1;
}
/*
* pg_b64_decode
*
* Decode the given base64 string. Returns the length of the decoded
* string on success, and -1 in the event of an error with the result
* buffer zeroed for safety.
*/
int
pg_b64_decode(const char *src, int len, char *dst, int dstlen)
{
const char *srcend = src + len,
*s = src;
char *p = dst;
char c;
int b = 0;
uint32 buf = 0;
int pos = 0,
end = 0;
while (s < srcend)
{
c = *s++;
/* Leave if a whitespace is found */
if (c == ' ' || c == '\t' || c == '\n' || c == '\r')
goto error;
if (c == '=')
{
/* end sequence */
if (!end)
{
if (pos == 2)
end = 1;
else if (pos == 3)
end = 2;
else
{
/*
* Unexpected "=" character found while decoding base64
* sequence.
*/
goto error;
}
}
b = 0;
}
else
{
b = -1;
if (c > 0 && c < 127)
b = b64lookup[(unsigned char) c];
if (b < 0)
{
/* invalid symbol found */
goto error;
}
}
/* add it to buffer */
buf = (buf << 6) + b;
pos++;
if (pos == 4)
{
/*
* Leave if there is an overflow in the area allocated for the
* decoded string.
*/
if ((p - dst + 1) > dstlen)
goto error;
*p++ = (buf >> 16) & 255;
if (end == 0 || end > 1)
{
/* overflow check */
if ((p - dst + 1) > dstlen)
goto error;
*p++ = (buf >> 8) & 255;
}
if (end == 0 || end > 2)
{
/* overflow check */
if ((p - dst + 1) > dstlen)
goto error;
*p++ = buf & 255;
}
buf = 0;
pos = 0;
}
}
if (pos != 0)
{
/*
* base64 end sequence is invalid. Input data is missing padding, is
* truncated or is otherwise corrupted.
*/
goto error;
}
Assert((p - dst) <= dstlen);
return p - dst;
error:
memset(dst, 0, dstlen);
return -1;
}
/*
* pg_b64_enc_len
*
* Returns to caller the length of the string if it were encoded with
* base64 based on the length provided by caller. This is useful to
* estimate how large a buffer allocation needs to be done before doing
* the actual encoding.
*/
int
pg_b64_enc_len(int srclen)
{
/* 3 bytes will be converted to 4 */
return (srclen + 2) / 3 * 4;
}
/*
* pg_b64_dec_len
*
* Returns to caller the length of the string if it were to be decoded
* with base64, based on the length given by caller. This is useful to
* estimate how large a buffer allocation needs to be done before doing
* the actual decoding.
*/
int
pg_b64_dec_len(int srclen)
{
return (srclen * 3) >> 2;
}
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