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base94 encoder/decoder
#include "base94.h"
void base94_encode(const unsigned char *plain, unsigned char *code) {
// high * 2^64 | low
unsigned long long value
= ((unsigned long long)plain[1] << 56) | ((unsigned long long)plain[2] << 48)
| ((unsigned long long)plain[3] << 40) | ((unsigned long long)plain[4] << 32)
| ((unsigned long)plain[5] << 24) | ((unsigned long)plain[6] << 16)
| ((unsigned long)plain[7] << 8) | plain[8];
unsigned long remainder;
int i;
// 2^64 = 2087680406712262 * 94^2 + 4584
remainder = value % 8836 + (unsigned long)plain[0] * 4584;
value = value / 8836 + plain[0] * 2087680406712262ul;
code[10] = 33 + remainder % 94;
remainder /= 94;
code[9] = 33 + remainder % 94;
value += remainder / 94;
for (i = 8; i >= 0; --i) {
code[i] = 33 + value % 94;
value /= 94;
}
}
void base94_decode(const unsigned char *code, unsigned char *plain) {
// high * 94^9 | low
unsigned long long value = 0;
unsigned long high;
int i;
for (i = 2; i < 11; ++i) {
value *= 94;
value += code[i] - 33;
}
high = (code[0] - 33) * 94 + (code[1] - 33);
// 94^9 = 2238260946205534 * 2^8
plain[8] = value & 0xff;
value >>= 8;
value += high * 2238260946205534;
plain[0] = (value >> 56) & 0xff;
plain[1] = (value >> 48) & 0xff;
plain[2] = (value >> 40) & 0xff;
plain[3] = (value >> 32) & 0xff;
plain[4] = (value >> 24) & 0xff;
plain[5] = (value >> 16) & 0xff;
plain[6] = (value >> 8) & 0xff;
plain[7] = value & 0xff;
}
#include <limits.h>
#if UCHAR_MAX != 255
#error sizeof (char) != 1
#endif
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#if defined(__MSDOS__) || defined(_WIN32)
# include <io.h>
# include <fcntl.h>
#endif
#include "base94.h"
#define MODE_AUTO 0
#define MODE_ENCODE 1
#define MODE_DECODE 2
#define BASE94_EXTENSION ".b94"
static const int ENCODE_SIZE_MAP[] = { 0, 2, 3, 4, 5, 7, 8, 9, 10, 11, };
static const int DECODE_SIZE_MAP[] = { 0, 0, 1, 2, 3, 4, 4, 5, 6, 7, 8, 9 };
static const char* PROGRAM;
int base94_encode_stream(FILE *input, FILE *output, int max_line_length) {
int error;
unsigned char plain[9];
unsigned char code[11];
size_t size;
unsigned int i;
int line_length = 0;
for (; ; ) {
// input
size = fread(plain, 1, sizeof plain, input);
if (ferror(input)) {
error = errno;
fprintf(stderr, "%s: can't read data.\n", PROGRAM);
return error;
}
if (size == 0) {
break;
}
if (size < sizeof plain) {
memset(plain + (sizeof plain - size), 0, sizeof plain - size);
}
// encode
base94_encode(plain, code);
size = ENCODE_SIZE_MAP[size];
// output
for (i = 0; i < size; ++i) {
if (putc(code[i], output) == EOF) {
if (ferror(output)) {
error = errno;
} else {
error = EIO;
}
fprintf(stderr, "%s: can't write data.\n", PROGRAM);
return error;
}
if (max_line_length > 0) {
++line_length;
if (line_length >= max_line_length) {
if (putc('\n', output) == EOF) {
if (ferror(output)) {
error = errno;
} else {
error = EIO;
}
fprintf(stderr, "%s: can't write data.\n", PROGRAM);
return error;
}
line_length = 0;
}
}
}
//result = fwrite(code, 1, size, output);
//if (ferror(output)) {
// error = errno;
// fprintf(stderr, "%s: can't write data.\n", PROGRAM);
// return error;
//}
//if (size != result) {
// fprintf(stderr, "%s: can't write data completely.\n", PROGRAM);
// return EIO;
//}
}
return 0;
}
int base94_decode_stream(FILE *input, FILE *output) {
int error;
unsigned char plain[9];
unsigned char code[11];
size_t size, result;
int c;
for (; ; ) {
// input
// collect 11 characters
size = 0;
while (size < sizeof code) {
c = getc(input);
if (c == EOF) {
if (ferror(input)) {
error = errno;
fprintf(stderr, "%s: can't read data.\n", PROGRAM);
return error;
}
break; // EOF
}
if (c >= 33 && c <= 126) {
code[size] = (unsigned char)c;
++size;
} else if (c == ' ' || c == '\t' || c == '\r' || c == '\n') {
// skip
} else {
fprintf(stderr, "%s: invalid base94 byte %d, skipped.\n", PROGRAM, c);
}
}
if (size == 0) {
break;
}
if (size < sizeof code) {
memset(code + size, 126, sizeof code - size);
}
// decode
base94_decode(code, plain);
size = DECODE_SIZE_MAP[size];
// output
result = fwrite(plain, 1, size, output);
if (ferror(output)) {
error = errno;
fprintf(stderr, "%s: can't write data.\n", PROGRAM);
return error;
}
if (size != result) {
fprintf(stderr, "%s: can't write data completely.\n", PROGRAM);
return EIO;
}
}
return 0;
}
/*
int test() {
unsigned char plain[9];
unsigned char plain2[9];
unsigned char code[11];
int i, j;
int total = 0, bad = 0;
srand(0);
memset(plain, 0, 9);
for (i = 0; i < 1000000; ++i) {
for (j = 0; j < 9; ++j) {
plain[j] = rand() & 0xff;
}
base94_encode(plain, code);
base94_decode(code, plain2);
if (memcmp(plain, plain2, 9) != 0) {
printf("%02x %02x %02x %02x %02x %02x %02x %02x %02x -",
plain[0], plain[1], plain[2], plain[3], plain[4], plain[5], plain[6], plain[7], plain[8], plain[9]);
printf("%02x %02x %02x %02x %02x %02x %02x %02x %02x\n",
plain2[0], plain2[1], plain2[2], plain2[3], plain2[4], plain2[5], plain2[6], plain2[7], plain2[8], plain2[9]);
}
}
for (i = 0; i < 1000000; ++i) {
for (j = 0; j < 9; ++j) {
plain[j] = rand() & 0xff;
}
for (j = 8; j > 0; --j) { // 8-1
plain[j] = 0;
base94_encode(plain, code);
memset(code + ENCODE_SIZE_MAP[j], 126, sizeof code - ENCODE_SIZE_MAP[j]);
base94_decode(code, plain2);
++total;
if (memcmp(plain, plain2, j) != 0) {
printf("%d: %02x %02x %02x %02x %02x %02x %02x %02x %02x - ",
j, plain[0], plain[1], plain[2], plain[3], plain[4], plain[5], plain[6], plain[7], plain[8], plain[9]);
printf("%02x %02x %02x %02x %02x %02x %02x %02x %02x\n",
plain2[0], plain2[1], plain2[2], plain2[3], plain2[4], plain2[5], plain2[6], plain2[7], plain2[8], plain2[9]);
++bad;
}
}
}
printf("Total: %d, Bad: %d\n", total, bad);
puts("Press enter to exit,\n");
getchar();
return 0;
}
*/
int main(int argc, char *argv[]) {
FILE *in = stdin;
FILE *out = stdout;
FILE *in_file = NULL;
FILE *out_file = NULL;
int error = 0;
int mode = MODE_AUTO;
PROGRAM = strrchr(argv[0], '\\');
if (PROGRAM) {
++PROGRAM;
} else {
PROGRAM = argv[0];
}
// return test();
if (argc == 2) {
const char *source = argv[1];
char destination[256];
// strip directory components
const char *extension = strrchr(source, '\\');
if (extension) {
++extension;
} else {
extension = source;
}
// delect extension
extension = strrchr(extension, '.');
if (extension) {
mode = _stricmp(extension, BASE94_EXTENSION) == 0 ? MODE_DECODE : MODE_ENCODE;
} else {
mode = MODE_ENCODE;
}
if (mode == MODE_DECODE) {
// decode
strcpy(destination, source);
destination[strlen(source) - strlen(BASE94_EXTENSION)] = '\0'; // strip .b94
} else {
// encode
strcpy(destination, source);
strcat(destination, BASE94_EXTENSION); // append .b94
}
in_file = fopen(source, "r");
if (in_file == NULL) {
error = errno;
fprintf(stderr, "%s: can't open file '%s'.\n", PROGRAM, source);
return error;
}
out_file = fopen(destination, "w");
if (out_file == NULL) {
error = errno;
fprintf(stderr, "%s: can't open file '%s'.\n", PROGRAM, destination);
fclose(out_file);
return error;
}
in = in_file;
out = out_file;
}
if (mode == MODE_AUTO) {
if (_stricmp(PROGRAM, "unbase94") == 0 || _stricmp(PROGRAM, "unbase94.exe") == 0) {
mode = MODE_DECODE;
} else {
mode = MODE_ENCODE;
}
}
switch (mode) {
case MODE_ENCODE:
/* set to binary mode for Windows */
#if defined(__MSDOS__) || defined(_WIN32)
if (_setmode(_fileno(in), _O_BINARY) == -1) {
fprintf(stderr, "%s: can't change input to binary mode.\n", PROGRAM);
return EIO;
}
#endif
error = base94_encode_stream(in, out, 76);
break;
case MODE_DECODE:
/* set to binary mode for Windows */
#if defined(__MSDOS__) || defined(_WIN32)
if (_setmode(_fileno(out), _O_BINARY) == -1) {
fprintf(stderr, "%s: can't change output to binary mode.\n", PROGRAM);
return EIO;
}
#endif
error = base94_decode_stream(in, out);
break;
}
if (in_file) {
fclose(in_file);
}
if (out_file) {
fclose(out_file);
}
return error;
}
@pjdennis

This comment has been minimized.

pjdennis commented Sep 23, 2016

There appears to be an error on line 55 of base94_msvc.c which reads:

memset(plain + (sizeof plain - size), 0, sizeof plain - size);

I believe it is supposed to be clearing all the bytes of plain that were not read (i.e. those starting at plain + size.) I suggest this is the correct code:

memset(plain + size, 0, sizeof plain - size);

Otherwise thanks to the poster, this was a great starting point for a C# implementation.

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