encode.c

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/*-------------------------------------------------------------------------
 *
 * encode.c
 *    Various data encoding/decoding things.
 *
 * Copyright (c) 2001-2026, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/encode.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include <ctype.h>
 
#include "mb/pg_wchar.h"
#include "port/simd.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "varatt.h"
 
 
/*
 * Encoding conversion API.
 * encode_len() and decode_len() compute the amount of space needed, while
 * encode() and decode() perform the actual conversions.  It is okay for
 * the _len functions to return an overestimate, but not an underestimate.
 * (Having said that, large overestimates could cause unnecessary errors,
 * so it's better to get it right.)  The conversion routines write to the
 * buffer at *res and return the true length of their output.
 */
struct pg_encoding
{
    uint64      (*encode_len) (const char *data, size_t dlen);
    uint64      (*decode_len) (const char *data, size_t dlen);
    uint64      (*encode) (const char *data, size_t dlen, char *res);
    uint64      (*decode) (const char *data, size_t dlen, char *res);
};
 
static const struct pg_encoding *pg_find_encoding(const char *name);
 
/*
 * SQL functions.
 */
 
Datum
binary_encode(PG_FUNCTION_ARGS)
{
    bytea      *data = PG_GETARG_BYTEA_PP(0);
    Datum       name = PG_GETARG_DATUM(1);
    text       *result;
    char       *namebuf;
    char       *dataptr;
    size_t      datalen;
    uint64      resultlen;
    uint64      res;
    const struct pg_encoding *enc;
 
    namebuf = TextDatumGetCString(name);
 
    enc = pg_find_encoding(namebuf);
    if (enc == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("unrecognized encoding: \"%s\"", namebuf),
                 errhint("Valid encodings are \"%s\", \"%s\", \"%s\", \"%s\", and \"%s\".",
                         "base32hex", "base64", "base64url", "escape", "hex")));
 
    dataptr = VARDATA_ANY(data);
    datalen = VARSIZE_ANY_EXHDR(data);
 
    resultlen = enc->encode_len(dataptr, datalen);
 
    /*
     * resultlen possibly overflows uint32, therefore on 32-bit machines it's
     * unsafe to rely on palloc's internal check.
     */
    if (resultlen > MaxAllocSize - VARHDRSZ)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("result of encoding conversion is too large")));
 
    result = palloc(VARHDRSZ + resultlen);
 
    res = enc->encode(dataptr, datalen, VARDATA(result));
 
    /* Make this FATAL 'cause we've trodden on memory ... */
    if (res > resultlen)
        elog(FATAL, "overflow - encode estimate too small");
 
    SET_VARSIZE(result, VARHDRSZ + res);
 
    PG_RETURN_TEXT_P(result);
}
 
Datum
binary_decode(PG_FUNCTION_ARGS)
{
    text       *data = PG_GETARG_TEXT_PP(0);
    Datum       name = PG_GETARG_DATUM(1);
    bytea      *result;
    char       *namebuf;
    char       *dataptr;
    size_t      datalen;
    uint64      resultlen;
    uint64      res;
    const struct pg_encoding *enc;
 
    namebuf = TextDatumGetCString(name);
 
    enc = pg_find_encoding(namebuf);
    if (enc == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("unrecognized encoding: \"%s\"", namebuf),
                 errhint("Valid encodings are \"%s\", \"%s\", \"%s\", \"%s\", and \"%s\".",
                         "base32hex", "base64", "base64url", "escape", "hex")));
 
    dataptr = VARDATA_ANY(data);
    datalen = VARSIZE_ANY_EXHDR(data);
 
    resultlen = enc->decode_len(dataptr, datalen);
 
    /*
     * resultlen possibly overflows uint32, therefore on 32-bit machines it's
     * unsafe to rely on palloc's internal check.
     */
    if (resultlen > MaxAllocSize - VARHDRSZ)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("result of decoding conversion is too large")));
 
    result = palloc(VARHDRSZ + resultlen);
 
    res = enc->decode(dataptr, datalen, VARDATA(result));
 
    /* Make this FATAL 'cause we've trodden on memory ... */
    if (res > resultlen)
        elog(FATAL, "overflow - decode estimate too small");
 
    SET_VARSIZE(result, VARHDRSZ + res);
 
    PG_RETURN_BYTEA_P(result);
}
 
 
/*
 * HEX
 */
 
/*
 * The hex expansion of each possible byte value (two chars per value).
 */
static const char hextbl[512] =
"000102030405060708090a0b0c0d0e0f"
"101112131415161718191a1b1c1d1e1f"
"202122232425262728292a2b2c2d2e2f"
"303132333435363738393a3b3c3d3e3f"
"404142434445464748494a4b4c4d4e4f"
"505152535455565758595a5b5c5d5e5f"
"606162636465666768696a6b6c6d6e6f"
"707172737475767778797a7b7c7d7e7f"
"808182838485868788898a8b8c8d8e8f"
"909192939495969798999a9b9c9d9e9f"
"a0a1a2a3a4a5a6a7a8a9aaabacadaeaf"
"b0b1b2b3b4b5b6b7b8b9babbbcbdbebf"
"c0c1c2c3c4c5c6c7c8c9cacbcccdcecf"
"d0d1d2d3d4d5d6d7d8d9dadbdcdddedf"
"e0e1e2e3e4e5e6e7e8e9eaebecedeeef"
"f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff";
 
static const int8 hexlookup[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, -1, -1, -1, -1, -1,
    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, 10, 11, 12, 13, 14, 15, -1, -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 inline uint64
hex_encode_scalar(const char *src, size_t len, char *dst)
{
    const char *end = src + len;
 
    while (src < end)
    {
        unsigned char usrc = *((const unsigned char *) src);
 
        memcpy(dst, &hextbl[2 * usrc], 2);
        src++;
        dst += 2;
    }
    return (uint64) len * 2;
}
 
uint64
hex_encode(const char *src, size_t len, char *dst)
{
#ifdef USE_NO_SIMD
    return hex_encode_scalar(src, len, dst);
#else
    const uint64 tail_idx = len & ~(sizeof(Vector8) - 1);
    uint64      i;
 
    /*
     * This splits the high and low nibbles of each byte into separate
     * vectors, adds the vectors to a mask that converts the nibbles to their
     * equivalent ASCII bytes, and interleaves those bytes back together to
     * form the final hex-encoded string.
     */
    for (i = 0; i < tail_idx; i += sizeof(Vector8))
    {
        Vector8     srcv;
        Vector8     lo;
        Vector8     hi;
        Vector8     mask;
 
        vector8_load(&srcv, (const uint8 *) &src[i]);
 
        lo = vector8_and(srcv, vector8_broadcast(0x0f));
        mask = vector8_gt(lo, vector8_broadcast(0x9));
        mask = vector8_and(mask, vector8_broadcast('a' - '0' - 10));
        mask = vector8_add(mask, vector8_broadcast('0'));
        lo = vector8_add(lo, mask);
 
        hi = vector8_and(srcv, vector8_broadcast(0xf0));
        hi = vector8_shift_right(hi, 4);
        mask = vector8_gt(hi, vector8_broadcast(0x9));
        mask = vector8_and(mask, vector8_broadcast('a' - '0' - 10));
        mask = vector8_add(mask, vector8_broadcast('0'));
        hi = vector8_add(hi, mask);
 
        vector8_store((uint8 *) &dst[i * 2],
                      vector8_interleave_low(hi, lo));
        vector8_store((uint8 *) &dst[i * 2 + sizeof(Vector8)],
                      vector8_interleave_high(hi, lo));
    }
 
    (void) hex_encode_scalar(src + i, len - i, dst + i * 2);
 
    return (uint64) len * 2;
#endif
}
 
static inline bool
get_hex(const char *cp, char *out)
{
    unsigned char c = (unsigned char) *cp;
    int         res = -1;
 
    if (c < 127)
        res = hexlookup[c];
 
    *out = (char) res;
 
    return (res >= 0);
}
 
uint64
hex_decode(const char *src, size_t len, char *dst)
{
    return hex_decode_safe(src, len, dst, NULL);
}
 
static inline uint64
hex_decode_safe_scalar(const char *src, size_t len, char *dst, Node *escontext)
{
    const char *s,
               *srcend;
    char        v1,
                v2,
               *p;
 
    srcend = src + len;
    s = src;
    p = dst;
    while (s < srcend)
    {
        if (*s == ' ' || *s == '\n' || *s == '\t' || *s == '\r')
        {
            s++;
            continue;
        }
        if (!get_hex(s, &v1))
            ereturn(escontext, 0,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("invalid hexadecimal digit: \"%.*s\"",
                            pg_mblen_range(s, srcend), s)));
        s++;
        if (s >= srcend)
            ereturn(escontext, 0,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("invalid hexadecimal data: odd number of digits")));
        if (!get_hex(s, &v2))
            ereturn(escontext, 0,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("invalid hexadecimal digit: \"%.*s\"",
                            pg_mblen_range(s, srcend), s)));
        s++;
        *p++ = (v1 << 4) | v2;
    }
 
    return p - dst;
}
 
/*
 * This helper converts each byte to its binary-equivalent nibble by
 * subtraction and combines them to form the return bytes (separated by zero
 * bytes).  Returns false if any input bytes are outside the expected ranges of
 * ASCII values.  Otherwise, returns true.
 */
#ifndef USE_NO_SIMD
static inline bool
hex_decode_simd_helper(const Vector8 src, Vector8 *dst)
{
    Vector8     sub;
    Vector8     mask_hi = vector8_interleave_low(vector8_broadcast(0), vector8_broadcast(0x0f));
    Vector8     mask_lo = vector8_interleave_low(vector8_broadcast(0x0f), vector8_broadcast(0));
    Vector8     tmp;
    bool        ret;
 
    tmp = vector8_gt(vector8_broadcast('9' + 1), src);
    sub = vector8_and(tmp, vector8_broadcast('0'));
 
    tmp = vector8_gt(src, vector8_broadcast('A' - 1));
    tmp = vector8_and(tmp, vector8_broadcast('A' - 10));
    sub = vector8_add(sub, tmp);
 
    tmp = vector8_gt(src, vector8_broadcast('a' - 1));
    tmp = vector8_and(tmp, vector8_broadcast('a' - 'A'));
    sub = vector8_add(sub, tmp);
 
    *dst = vector8_issub(src, sub);
    ret = !vector8_has_ge(*dst, 0x10);
 
    tmp = vector8_and(*dst, mask_hi);
    tmp = vector8_shift_right(tmp, 8);
    *dst = vector8_and(*dst, mask_lo);
    *dst = vector8_shift_left(*dst, 4);
    *dst = vector8_or(*dst, tmp);
    return ret;
}
#endif                          /* ! USE_NO_SIMD */
 
uint64
hex_decode_safe(const char *src, size_t len, char *dst, Node *escontext)
{
#ifdef USE_NO_SIMD
    return hex_decode_safe_scalar(src, len, dst, escontext);
#else
    const uint64 tail_idx = len & ~(sizeof(Vector8) * 2 - 1);
    uint64      i;
    bool        success = true;
 
    /*
     * We must process 2 vectors at a time since the output will be half the
     * length of the input.
     */
    for (i = 0; i < tail_idx; i += sizeof(Vector8) * 2)
    {
        Vector8     srcv;
        Vector8     dstv1;
        Vector8     dstv2;
 
        vector8_load(&srcv, (const uint8 *) &src[i]);
        success &= hex_decode_simd_helper(srcv, &dstv1);
 
        vector8_load(&srcv, (const uint8 *) &src[i + sizeof(Vector8)]);
        success &= hex_decode_simd_helper(srcv, &dstv2);
 
        vector8_store((uint8 *) &dst[i / 2], vector8_pack_16(dstv1, dstv2));
    }
 
    /*
     * If something didn't look right in the vector path, try again in the
     * scalar path so that we can handle it correctly.
     */
    if (!success)
        i = 0;
 
    return i / 2 + hex_decode_safe_scalar(src + i, len - i, dst + i / 2, escontext);
#endif
}
 
static uint64
hex_enc_len(const char *src, size_t srclen)
{
    return (uint64) srclen << 1;
}
 
static uint64
hex_dec_len(const char *src, size_t srclen)
{
    return (uint64) srclen >> 1;
}
 
/*
 * BASE64 and BASE64URL
 */
 
static const char _base64[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
static const char _base64url[] =
"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_base64_encode_internal
 *
 * Helper for decoding base64 or base64url.  When url is passed as true the
 * input will be encoded using base64url.  len bytes in src is encoded into
 * dst.
 */
static uint64
pg_base64_encode_internal(const char *src, size_t len, char *dst, bool url)
{
    char       *p,
               *lend = dst + 76;
    const char *s,
               *end = src + len;
    int         pos = 2;
    uint32      buf = 0;
    const char *alphabet = url ? _base64url : _base64;
 
    s = src;
    p = dst;
 
    while (s < end)
    {
        buf |= (unsigned char) *s << (pos << 3);
        pos--;
        s++;
 
        /* write it out */
        if (pos < 0)
        {
            *p++ = alphabet[(buf >> 18) & 0x3f];
            *p++ = alphabet[(buf >> 12) & 0x3f];
            *p++ = alphabet[(buf >> 6) & 0x3f];
            *p++ = alphabet[buf & 0x3f];
 
            pos = 2;
            buf = 0;
 
            if (!url && p >= lend)
            {
                *p++ = '\n';
                lend = p + 76;
            }
        }
    }
 
    /* Handle remaining bytes in buf */
    if (pos != 2)
    {
        *p++ = alphabet[(buf >> 18) & 0x3f];
        *p++ = alphabet[(buf >> 12) & 0x3f];
 
        if (pos == 0)
        {
            *p++ = alphabet[(buf >> 6) & 0x3f];
            if (!url)
                *p++ = '=';
        }
        else if (!url)
        {
            *p++ = '=';
            *p++ = '=';
        }
    }
 
    return p - dst;
}
 
static uint64
pg_base64_encode(const char *src, size_t len, char *dst)
{
    return pg_base64_encode_internal(src, len, dst, false);
}
 
static uint64
pg_base64url_encode(const char *src, size_t len, char *dst)
{
    return pg_base64_encode_internal(src, len, dst, true);
}
 
/*
 * pg_base64_decode_internal
 *
 * Helper for decoding base64 or base64url. When url is passed as true the
 * input will be assumed to be encoded using base64url.
 */
static uint64
pg_base64_decode_internal(const char *src, size_t len, char *dst, bool url)
{
    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++;
 
        if (c == ' ' || c == '\t' || c == '\n' || c == '\r')
            continue;
 
        /* convert base64url to base64 */
        if (url)
        {
            if (c == '-')
                c = '+';
            else if (c == '_')
                c = '/';
        }
 
        if (c == '=')
        {
            /* end sequence */
            if (!end)
            {
                if (pos == 2)
                    end = 1;
                else if (pos == 3)
                    end = 2;
                else
                {
                    /* translator: %s is the name of an encoding scheme */
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("unexpected \"=\" while decoding %s sequence", url ? "base64url" : "base64")));
                }
            }
            b = 0;
        }
        else
        {
            b = -1;
            if (c > 0 && c < 127)
                b = b64lookup[(unsigned char) c];
            if (b < 0)
            {
                /* translator: %s is the name of an encoding scheme */
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("invalid symbol \"%.*s\" found while decoding %s sequence",
                                pg_mblen_range(s - 1, srcend), s - 1,
                                url ? "base64url" : "base64")));
            }
        }
        /* add it to buffer */
        buf = (buf << 6) + b;
        pos++;
        if (pos == 4)
        {
            *p++ = (buf >> 16) & 255;
            if (end == 0 || end > 1)
                *p++ = (buf >> 8) & 255;
            if (end == 0 || end > 2)
                *p++ = buf & 255;
            buf = 0;
            pos = 0;
        }
    }
 
    if (pos == 2)
    {
        buf <<= 12;
        *p++ = (buf >> 16) & 0xFF;
    }
    else if (pos == 3)
    {
        buf <<= 6;
        *p++ = (buf >> 16) & 0xFF;
        *p++ = (buf >> 8) & 0xFF;
    }
    else if (pos != 0)
    {
        /* translator: %s is the name of an encoding scheme */
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("invalid %s end sequence", url ? "base64url" : "base64"),
                 errhint("Input data is missing padding, is truncated, or is otherwise corrupted.")));
    }
 
    return p - dst;
}
 
static uint64
pg_base64_decode(const char *src, size_t len, char *dst)
{
    return pg_base64_decode_internal(src, len, dst, false);
}
 
static uint64
pg_base64url_decode(const char *src, size_t len, char *dst)
{
    return pg_base64_decode_internal(src, len, dst, true);
}
 
static uint64
pg_base64_enc_len(const char *src, size_t srclen)
{
    /* 3 bytes will be converted to 4, linefeed after 76 chars */
    return ((uint64) srclen + 2) / 3 * 4 + (uint64) srclen / (76 * 3 / 4);
}
 
static uint64
pg_base64_dec_len(const char *src, size_t srclen)
{
    return ((uint64) srclen * 3) >> 2;
}
 
static uint64
pg_base64url_enc_len(const char *src, size_t srclen)
{
    /*
     * Unlike standard base64, base64url doesn't use padding characters when
     * the input length is not divisible by 3
     */
    return (srclen + 2) / 3 * 4;
}
 
static uint64
pg_base64url_dec_len(const char *src, size_t srclen)
{
    /*
     * For base64, each 4 characters of input produce at most 3 bytes of
     * output.  For base64url without padding, we need to round up to the
     * nearest 4
     */
    size_t      adjusted_len = srclen;
 
    if (srclen % 4 != 0)
        adjusted_len += 4 - (srclen % 4);
 
    return (adjusted_len * 3) / 4;
}
 
/*
 * Escape
 * Minimally escape bytea to text.
 * De-escape text to bytea.
 *
 * We must escape zero bytes and high-bit-set bytes to avoid generating
 * text that might be invalid in the current encoding, or that might
 * change to something else if passed through an encoding conversion
 * (leading to failing to de-escape to the original bytea value).
 * Also of course backslash itself has to be escaped.
 *
 * De-escaping processes \\ and any \### octal
 */
 
#define VAL(CH)         ((CH) - '0')
#define DIG(VAL)        ((VAL) + '0')
 
static uint64
esc_encode(const char *src, size_t srclen, char *dst)
{
    const char *end = src + srclen;
    char       *rp = dst;
    uint64      len = 0;
 
    while (src < end)
    {
        unsigned char c = (unsigned char) *src;
 
        if (c == '\0' || IS_HIGHBIT_SET(c))
        {
            rp[0] = '\\';
            rp[1] = DIG(c >> 6);
            rp[2] = DIG((c >> 3) & 7);
            rp[3] = DIG(c & 7);
            rp += 4;
            len += 4;
        }
        else if (c == '\\')
        {
            rp[0] = '\\';
            rp[1] = '\\';
            rp += 2;
            len += 2;
        }
        else
        {
            *rp++ = c;
            len++;
        }
 
        src++;
    }
 
    return len;
}
 
static uint64
esc_decode(const char *src, size_t srclen, char *dst)
{
    const char *end = src + srclen;
    char       *rp = dst;
    uint64      len = 0;
 
    while (src < end)
    {
        if (src[0] != '\\')
            *rp++ = *src++;
        else if (src + 3 < end &&
                 (src[1] >= '0' && src[1] <= '3') &&
                 (src[2] >= '0' && src[2] <= '7') &&
                 (src[3] >= '0' && src[3] <= '7'))
        {
            int         val;
 
            val = VAL(src[1]);
            val <<= 3;
            val += VAL(src[2]);
            val <<= 3;
            *rp++ = val + VAL(src[3]);
            src += 4;
        }
        else if (src + 1 < end &&
                 (src[1] == '\\'))
        {
            *rp++ = '\\';
            src += 2;
        }
        else
        {
            /*
             * One backslash, not followed by ### valid octal. Should never
             * get here, since esc_dec_len does same check.
             */
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                     errmsg("invalid input syntax for type %s", "bytea")));
        }
 
        len++;
    }
 
    return len;
}
 
static uint64
esc_enc_len(const char *src, size_t srclen)
{
    const char *end = src + srclen;
    uint64      len = 0;
 
    while (src < end)
    {
        if (*src == '\0' || IS_HIGHBIT_SET(*src))
            len += 4;
        else if (*src == '\\')
            len += 2;
        else
            len++;
 
        src++;
    }
 
    return len;
}
 
static uint64
esc_dec_len(const char *src, size_t srclen)
{
    const char *end = src + srclen;
    uint64      len = 0;
 
    while (src < end)
    {
        if (src[0] != '\\')
            src++;
        else if (src + 3 < end &&
                 (src[1] >= '0' && src[1] <= '3') &&
                 (src[2] >= '0' && src[2] <= '7') &&
                 (src[3] >= '0' && src[3] <= '7'))
        {
            /*
             * backslash + valid octal
             */
            src += 4;
        }
        else if (src + 1 < end &&
                 (src[1] == '\\'))
        {
            /*
             * two backslashes = backslash
             */
            src += 2;
        }
        else
        {
            /*
             * one backslash, not followed by ### valid octal
             */
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                     errmsg("invalid input syntax for type %s", "bytea")));
        }
 
        len++;
    }
    return len;
}
 
/*
 * BASE32HEX
 */
 
static const char base32hex_table[] = "0123456789ABCDEFGHIJKLMNOPQRSTUV";
 
static const int8 b32hexlookup[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, -1, -1, -1, -1, -1,
    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
    -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
    25, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
    25, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};
 
static uint64
base32hex_enc_len(const char *src, size_t srclen)
{
    /* 5 bytes encode to 8 characters, round up to multiple of 8 for padding */
    return ((uint64) srclen + 4) / 5 * 8;
}
 
static uint64
base32hex_dec_len(const char *src, size_t srclen)
{
    /* Each 8 characters of input produces at most 5 bytes of output */
    return ((uint64) srclen * 5) / 8;
}
 
static uint64
base32hex_encode(const char *src, size_t srclen, char *dst)
{
    const unsigned char *data = (const unsigned char *) src;
    uint32      bits_buffer = 0;
    int         bits_in_buffer = 0;
    uint64      output_pos = 0;
    size_t      i;
 
    for (i = 0; i < srclen; i++)
    {
        /* Add 8 bits to the buffer */
        bits_buffer = (bits_buffer << 8) | data[i];
        bits_in_buffer += 8;
 
        /* Extract 5-bit chunks while we have enough bits */
        while (bits_in_buffer >= 5)
        {
            bits_in_buffer -= 5;
            /* Extract top 5 bits */
            dst[output_pos++] = base32hex_table[(bits_buffer >> bits_in_buffer) & 0x1F];
            /* Clear the extracted bits by masking */
            bits_buffer &= ((1U << bits_in_buffer) - 1);
        }
    }
 
    /* Handle remaining bits (if any) */
    if (bits_in_buffer > 0)
        dst[output_pos++] = base32hex_table[(bits_buffer << (5 - bits_in_buffer)) & 0x1F];
 
    /* Add padding to make length a multiple of 8 (per RFC 4648) */
    while (output_pos % 8 != 0)
        dst[output_pos++] = '=';
 
    return output_pos;
}
 
static uint64
base32hex_decode(const char *src, size_t srclen, char *dst)
{
    const char *srcend = src + srclen,
               *s = src;
    uint32      bits_buffer = 0;
    int         bits_in_buffer = 0;
    uint64      output_pos = 0;
    int         pos = 0;        /* position within 8-character group (0-7) */
    bool        end = false;    /* have we seen padding? */
 
    while (s < srcend)
    {
        char        c = *s++;
        int         val;
 
        /* Skip whitespace */
        if (c == ' ' || c == '\t' || c == '\n' || c == '\r')
            continue;
 
        if (c == '=')
        {
            /*
             * The first padding is only valid at positions 2, 4, 5, or 7
             * within an 8-character group (corresponding to 1, 2, 3, or 4
             * input bytes). We only check the position for the first '='
             * character.
             */
            if (!end)
            {
                if (pos != 2 && pos != 4 && pos != 5 && pos != 7)
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("unexpected \"=\" while decoding base32hex sequence")));
                end = true;
            }
            pos++;
            continue;
        }
 
        /* No data characters allowed after padding */
        if (end)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("invalid symbol \"%.*s\" found while decoding base32hex sequence",
                            pg_mblen_range(s - 1, srcend), s - 1)));
 
        /* Decode base32hex character (0-9, A-V, case-insensitive) */
        val = -1;
        if ((unsigned char) c < 128)
            val = b32hexlookup[(unsigned char) c];
        if (val < 0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("invalid symbol \"%.*s\" found while decoding base32hex sequence",
                            pg_mblen_range(s - 1, srcend), s - 1)));
 
        /* Add 5 bits to buffer */
        bits_buffer = (bits_buffer << 5) | val;
        bits_in_buffer += 5;
        pos++;
 
        /* Extract 8-bit bytes when we have enough bits */
        while (bits_in_buffer >= 8)
        {
            bits_in_buffer -= 8;
            dst[output_pos++] = (unsigned char) (bits_buffer >> bits_in_buffer);
            /* Clear the extracted bits */
            bits_buffer &= ((1U << bits_in_buffer) - 1);
        }
 
        /* Reset position after each complete 8-character group */
        if (pos == 8)
            pos = 0;
    }
 
    return output_pos;
}
 
/*
 * Common
 */
 
static const struct
{
    const char *name;
    struct pg_encoding enc;
}           enclist[] =
 
{
    {
        "hex",
        {
            hex_enc_len, hex_dec_len, hex_encode, hex_decode
        }
    },
    {
        "base64",
        {
            pg_base64_enc_len, pg_base64_dec_len, pg_base64_encode, pg_base64_decode
        }
    },
    {
        "base64url",
        {
            pg_base64url_enc_len, pg_base64url_dec_len, pg_base64url_encode, pg_base64url_decode
        }
    },
    {
        "base32hex",
        {
            base32hex_enc_len, base32hex_dec_len, base32hex_encode, base32hex_decode
        }
    },
    {
        "escape",
        {
            esc_enc_len, esc_dec_len, esc_encode, esc_decode
        }
    },
    {
        NULL,
        {
            NULL, NULL, NULL, NULL
        }
    }
};
 
static const struct pg_encoding *
pg_find_encoding(const char *name)
{
    int         i;
 
    for (i = 0; enclist[i].name; i++)
        if (pg_strcasecmp(enclist[i].name, name) == 0)
            return &enclist[i].enc;
 
    return NULL;
}