94 lines
2.2 KiB
C
94 lines
2.2 KiB
C
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/**
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* `encode.c' - b64
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*
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* copyright (c) 2014 joseph werle
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include "b64.h"
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#ifdef b64_USE_CUSTOM_MALLOC
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extern void* b64_malloc(size_t);
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#endif
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#ifdef b64_USE_CUSTOM_REALLOC
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extern void* b64_realloc(void*, size_t);
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#endif
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char *
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b64_encode (const unsigned char *src, size_t len) {
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int i = 0;
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int j = 0;
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b64_buffer_t encbuf;
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size_t size = 0;
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unsigned char buf[4];
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unsigned char tmp[3];
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// alloc
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if(b64_buf_malloc(&encbuf) == -1) { return NULL; }
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// parse until end of source
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while (len--) {
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// read up to 3 bytes at a time into `tmp'
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tmp[i++] = *(src++);
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// if 3 bytes read then encode into `buf'
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if (3 == i) {
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buf[0] = (tmp[0] & 0xfc) >> 2;
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buf[1] = ((tmp[0] & 0x03) << 4) + ((tmp[1] & 0xf0) >> 4);
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buf[2] = ((tmp[1] & 0x0f) << 2) + ((tmp[2] & 0xc0) >> 6);
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buf[3] = tmp[2] & 0x3f;
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// allocate 4 new byts for `enc` and
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// then translate each encoded buffer
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// part by index from the base 64 index table
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// into `encbuf.ptr' unsigned char array
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if (b64_buf_realloc(&encbuf, size + 4) == -1) return NULL;
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for (i = 0; i < 4; ++i) {
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encbuf.ptr[size++] = b64_table[buf[i]];
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}
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// reset index
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i = 0;
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}
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}
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// remainder
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if (i > 0) {
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// fill `tmp' with `\0' at most 3 times
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for (j = i; j < 3; ++j) {
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tmp[j] = '\0';
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}
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// perform same codec as above
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buf[0] = (tmp[0] & 0xfc) >> 2;
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buf[1] = ((tmp[0] & 0x03) << 4) + ((tmp[1] & 0xf0) >> 4);
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buf[2] = ((tmp[1] & 0x0f) << 2) + ((tmp[2] & 0xc0) >> 6);
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buf[3] = tmp[2] & 0x3f;
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// perform same write to `encbuf->ptr` with new allocation
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for (j = 0; (j < i + 1); ++j) {
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if (b64_buf_realloc(&encbuf, size + 1) == -1) return NULL;
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encbuf.ptr[size++] = b64_table[buf[j]];
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}
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// while there is still a remainder
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// append `=' to `encbuf.ptr'
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while ((i++ < 3)) {
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if (b64_buf_realloc(&encbuf, size + 1) == -1) return NULL;
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encbuf.ptr[size++] = '=';
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}
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}
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// Make sure we have enough space to add '\0' character at end.
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if (b64_buf_realloc(&encbuf, size + 1) == -1) return NULL;
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encbuf.ptr[size] = '\0';
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return encbuf.ptr;
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}
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