basic: util - add base64mem() function similar to hexmem()
This implements RFC4648 for a slightly more compact representation of binary data compared to hex (6 bits per character rather than 4).
This commit is contained in:
Tom Gundersen
@@ -954,6 +954,180 @@ int unhexmem(const char *p, size_t l, void **mem, size_t *len) {
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return 0;
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}
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/* https://tools.ietf.org/html/rfc4648#section-4 */
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char base64char(int x) {
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static const char table[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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"abcdefghijklmnopqrstuvwxyz"
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"0123456789+/";
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return table[x & 63];
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}
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int unbase64char(char c) {
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unsigned offset;
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if (c >= 'A' && c <= 'Z')
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return c - 'A';
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offset = 'Z' - 'A' + 1;
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if (c >= 'a' && c <= 'z')
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return c - 'a' + offset;
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offset += 'z' - 'a' + 1;
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if (c >= '0' && c <= '9')
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return c - '0' + offset;
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offset += '9' - '0' + 1;
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if (c == '+')
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return offset;
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offset ++;
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if (c == '/')
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return offset;
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return -EINVAL;
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}
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char *base64mem(const void *p, size_t l) {
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char *r, *z;
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const uint8_t *x;
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/* three input bytes makes four output bytes, padding is added so we must round up */
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z = r = malloc(4 * (l + 2) / 3 + 1);
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if (!r)
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return NULL;
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for (x = p; x < (const uint8_t*) p + (l / 3) * 3; x += 3) {
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/* x[0] == XXXXXXXX; x[1] == YYYYYYYY; x[2] == ZZZZZZZZ */
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*(z++) = base64char(x[0] >> 2); /* 00XXXXXX */
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*(z++) = base64char((x[0] & 3) << 4 | x[1] >> 4); /* 00XXYYYY */
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*(z++) = base64char((x[1] & 15) << 2 | x[2] >> 6); /* 00YYYYZZ */
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*(z++) = base64char(x[2] & 63); /* 00ZZZZZZ */
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}
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switch (l % 3) {
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case 2:
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*(z++) = base64char(x[0] >> 2); /* 00XXXXXX */
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*(z++) = base64char((x[0] & 3) << 4 | x[1] >> 4); /* 00XXYYYY */
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*(z++) = base64char((x[1] & 15) << 2); /* 00YYYY00 */
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*(z++) = '=';
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break;
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case 1:
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*(z++) = base64char(x[0] >> 2); /* 00XXXXXX */
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*(z++) = base64char((x[0] & 3) << 4); /* 00XX0000 */
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*(z++) = '=';
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*(z++) = '=';
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break;
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}
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*z = 0;
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return r;
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}
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int unbase64mem(const char *p, size_t l, void **mem, size_t *_len) {
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_cleanup_free_ uint8_t *t = NULL;
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int a, b, c, d;
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uint8_t *r, *z;
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const char *x;
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size_t len;
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assert(p);
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/* padding ensures any base63 input has input divisible by 4 */
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if (l % 4 != 0)
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return -EINVAL;
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/* strip the padding */
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if (l > 0 && p[l - 1] == '=')
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l --;
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if (l > 0 && p[l - 1] == '=')
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l --;
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/* a group of four input bytes needs three output bytes, in case of
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padding we need to add two or three extra bytes */
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len = (l / 4) * 3 + (l % 4 ? (l % 4) - 1 : 0);
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z = r = malloc(len + 1);
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if (!r)
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return -ENOMEM;
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for (x = p; x < p + (l / 4) * 4; x += 4) {
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/* a == 00XXXXXX; b == 00YYYYYY; c == 00ZZZZZZ; d == 00WWWWWW */
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a = unbase64char(x[0]);
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if (a < 0)
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return -EINVAL;
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b = unbase64char(x[1]);
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if (b < 0)
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return -EINVAL;
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c = unbase64char(x[2]);
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if (c < 0)
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return -EINVAL;
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d = unbase64char(x[3]);
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if (d < 0)
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return -EINVAL;
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*(z++) = (uint8_t) a << 2 | (uint8_t) b >> 4; /* XXXXXXYY */
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*(z++) = (uint8_t) b << 4 | (uint8_t) c >> 2; /* YYYYZZZZ */
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*(z++) = (uint8_t) c << 6 | (uint8_t) d; /* ZZWWWWWW */
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}
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switch (l % 4) {
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case 3:
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a = unbase64char(x[0]);
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if (a < 0)
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return -EINVAL;
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b = unbase64char(x[1]);
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if (b < 0)
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return -EINVAL;
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c = unbase64char(x[2]);
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if (c < 0)
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return -EINVAL;
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/* c == 00ZZZZ00 */
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if (c & 3)
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return -EINVAL;
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*(z++) = (uint8_t) a << 2 | (uint8_t) b >> 4; /* XXXXXXYY */
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*(z++) = (uint8_t) b << 4 | (uint8_t) c >> 2; /* YYYYZZZZ */
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break;
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case 2:
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a = unbase64char(x[0]);
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if (a < 0)
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return -EINVAL;
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b = unbase64char(x[1]);
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if (b < 0)
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return -EINVAL;
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/* b == 00YY0000 */
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if (b & 15)
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return -EINVAL;
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*(z++) = (uint8_t) a << 2 | (uint8_t) (b >> 4); /* XXXXXXYY */
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break;
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}
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*z = 0;
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*mem = r;
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r = NULL;
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*_len = len;
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return 0;
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}
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char octchar(int x) {
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return '0' + (x & 7);
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}
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@@ -240,6 +240,8 @@ char octchar(int x) _const_;
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int unoctchar(char c) _const_;
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char decchar(int x) _const_;
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int undecchar(char c) _const_;
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char base64char(int x) _const_;
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int unbase64char(char c) _const_;
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char *cescape(const char *s);
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size_t cescape_char(char c, char *buf);
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@@ -616,6 +618,9 @@ static inline void *mempset(void *s, int c, size_t n) {
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char *hexmem(const void *p, size_t l);
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int unhexmem(const char *p, size_t l, void **mem, size_t *len);
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char *base64mem(const void *p, size_t l);
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int unbase64mem(const char *p, size_t l, void **mem, size_t *len);
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char *strextend(char **x, ...) _sentinel_;
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char *strrep(const char *s, unsigned n);
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