C语言版的Base-64加密解密函数的代码

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#include <stdint.h>
#include <stdlib.h>
#include <string.h>
static const char padding = '=';
static size_t digit_value(char ch);
    @description:
        Converts n bytes pointed to by src into base-64 representation.
{
    size_t partial_block_bytes = n % BLOCK_BYTE;
    size_t full_blocks = n / BLOCK_BYTE;
    if (!dst)
        return NULL;
    size_t k;
    for (k = 0; full_blocks--; bytes += BLOCK_BYTE) {
        check_append_newline(dst + k, &k);
        convert_block(dst, &k, bytes, BLOCK_BYTE);
    }
    check_append_newline(dst + k, &k);
    convert_block(dst, &k, bytes, partial_block_bytes);
    dst[k] = '0';
    return dst;
}
    @description:
        Converts a valid base-64 string into a decoded array of bytes
        and stores the number of decoded bytes in the object pointed
        to by n.
{
    size_t len = strlen(src);
    if (len % BLOCK_CHAR)
                free(dst);
            }
        }
        size_t encoded[] = {
            digit_value(src[0]),
            digit_value(src[1]),
            digit_value(src[2]),
            digit_value(src[3])
        };
            if (encoded[i] == (size_t)-1) {
                free(dst);
                return NULL;
            }
        }
        uint8_t bytes[] = {
            (encoded[0] << 2) + ((encoded[1] & 0x30) >> 4),
            ((encoded[1] & 0x0f) << 4) + ((encoded[2] & 0x3c) >> 2),
            ((encoded[2] & 0x03) << 6) + encoded[3]
        };
        for (size_t i = 0; i < BLOCK_BYTE; ++i) {
            if (bytes[i])
        }
    }
    return dst;
}
    @description:
        Locates the index value of a base-64 character for decoding.
static size_t digit_value(char ch)
{
    if (ch == padding)
        return 0;
    return p ? p - digits : (size_t)-1;
}
    @description:
        Appends a newline to dst if the value of end is at the correct
        position. Returns the updated value of end, which may not change
        if a newline was not appended.
{
        memcpy(dst, newline, NEWLINE_LEN);
    }
}
    @description:
        Converts a 24-bit block represented by 3 octets into four base-64
        characters and stores them in dst starting at end. Returns the 
        updated value of end for convenience.
{
    switch (bytes) {
        case 3:
            break;
        case 2:
            break;
        case 1:
            break;
    }
}
#define TEST_DRIVER
#ifdef TEST_DRIVER
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
    size_t n;
        free(p);
        free(q);
    }
    return 0;
}
#endif