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/* compressible_data_p.h -- generate compressible data
* Copyright (C) 2025 Hans Kristian Rosbach
* For conditions of distribution and use, see copyright notice in zlib.h
*/
#ifndef COMPRESSIBLE_DATA_P_H
#define COMPRESSIBLE_DATA_P_H
static inline size_t append_raw(uint8_t *dest, size_t size, const void *src, size_t len) {
if (len > size) len = size;
if (len == 0) return 0;
memcpy(dest, src, len);
return len;
}
static inline size_t append_str(uint8_t *dest, size_t size, const char *src) {
return append_raw(dest, size, src, strlen(src));
}
static inline size_t append_uint8_t(uint8_t *dest, size_t size, uint8_t src) {
return append_raw(dest, size, &src, 1);
}
// Alloc and initialize buffer with highly compressible data,
// interspersed with small amounts of random data and 3-byte matches.
static uint8_t *gen_compressible_data(size_t bufsize) {
const char teststr1[42] = "Hello hello World broken Test tast mello.";
const char teststr2[32] = "llollollollollo He Te me orld";
const char teststr3[4] = "bro";
int loops = 0;
uint8_t *buffer = (uint8_t *)malloc(bufsize);
if (buffer == NULL) {
return NULL;
}
for (size_t pos = 0; pos < bufsize; ) {
pos += append_str(buffer+pos, bufsize-pos, teststr1);
pos += append_uint8_t(buffer+pos, bufsize-pos, (uint8_t)(rand() & 0xFF));
// Every so often, add a few other little bits to break the pattern
if (loops % 13 == 0) {
pos += append_str(buffer+pos, bufsize-pos, teststr3);
pos += append_uint8_t(buffer+pos, bufsize-pos, (uint8_t)(rand() & 0xFF));
}
if (loops % 300 == 0) { // Only found once or twice per window
pos += append_str(buffer+pos, bufsize-pos, teststr2);
}
loops++;
}
if (bufsize > 0) {
buffer[bufsize-1] = 0;
}
return buffer;
}
#endif
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