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https://github.com/cesanta/mongoose.git
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94 lines
2.4 KiB
C
94 lines
2.4 KiB
C
#include "base64.h"
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static int mg_base64_encode_single(int c) {
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if (c < 26) {
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return c + 'A';
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} else if (c < 52) {
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return c - 26 + 'a';
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} else if (c < 62) {
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return c - 52 + '0';
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} else {
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return c == 62 ? '+' : '/';
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}
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}
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static int mg_base64_decode_single(int c) {
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if (c >= 'A' && c <= 'Z') {
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return c - 'A';
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} else if (c >= 'a' && c <= 'z') {
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return c + 26 - 'a';
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} else if (c >= '0' && c <= '9') {
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return c + 52 - '0';
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} else if (c == '+') {
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return 62;
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} else if (c == '/') {
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return 63;
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} else if (c == '=') {
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return 64;
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} else {
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return -1;
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}
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}
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size_t mg_base64_update(unsigned char ch, char *to, size_t n) {
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unsigned long rem = (n & 3) % 3;
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if (rem == 0) {
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to[n] = (char) mg_base64_encode_single(ch >> 2);
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to[++n] = (char) ((ch & 3) << 4);
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} else if (rem == 1) {
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to[n] = (char) mg_base64_encode_single(to[n] | (ch >> 4));
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to[++n] = (char) ((ch & 15) << 2);
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} else {
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to[n] = (char) mg_base64_encode_single(to[n] | (ch >> 6));
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to[++n] = (char) mg_base64_encode_single(ch & 63);
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n++;
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}
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return n;
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}
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size_t mg_base64_final(char *to, size_t n) {
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size_t saved = n;
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// printf("---[%.*s]\n", n, to);
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if (n & 3) n = mg_base64_update(0, to, n);
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if ((saved & 3) == 2) n--;
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// printf(" %d[%.*s]\n", n, n, to);
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while (n & 3) to[n++] = '=';
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to[n] = '\0';
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return n;
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}
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size_t mg_base64_encode(const unsigned char *p, size_t n, char *to, size_t dl) {
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size_t i, len = 0;
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if (dl > 0) to[0] = '\0';
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if (dl < ((n / 3) + (n % 3 ? 1 : 0)) * 4 + 1) return 0;
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for (i = 0; i < n; i++) len = mg_base64_update(p[i], to, len);
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len = mg_base64_final(to, len);
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return len;
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}
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size_t mg_base64_decode(const char *src, size_t n, char *dst, size_t dl) {
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const char *end = src == NULL ? NULL : src + n; // Cannot add to NULL
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size_t len = 0;
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if (dl < n / 4 * 3 + 1) goto fail;
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while (src != NULL && src + 3 < end) {
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int a = mg_base64_decode_single(src[0]),
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b = mg_base64_decode_single(src[1]),
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c = mg_base64_decode_single(src[2]),
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d = mg_base64_decode_single(src[3]);
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if (a == 64 || a < 0 || b == 64 || b < 0 || c < 0 || d < 0) {
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goto fail;
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}
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dst[len++] = (char) ((a << 2) | (b >> 4));
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if (src[2] != '=') {
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dst[len++] = (char) ((b << 4) | (c >> 2));
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if (src[3] != '=') dst[len++] = (char) ((c << 6) | d);
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}
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src += 4;
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}
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dst[len] = '\0';
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return len;
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fail:
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if (dl > 0) dst[0] = '\0';
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return 0;
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}
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