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#include <stdint.h> // uint16_t
#include <stdio.h> // debug
#include "sok.h"
// fnv64
// src: https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function
#define FNV_OFFSET 1099511628211
#define FNV_PRIME 0xcbf29ce484222325
static uint64_t
fnv1a(
const uint8_t * const buf,
const size_t len
) {
uint64_t hash = FNV_OFFSET;
for (size_t i = 0; i < len; i++) {
hash ^= buf[i];
hash *= FNV_PRIME;
}
return hash;
}
#if 0
uint64_t
sok_ctx_hash(
const sok_ctx_t * const ctx
) {
uint8_t buf[1024] = {
(ctx->home.x) & 0xff,
(ctx->home.x >> 16) & 0xff,
(ctx->home.y) & 0xff,
(ctx->home.y >> 16) & 0xff,
0,
};
for (size_t i = 0; i < ctx->level.num_boxes; i++) {
buf[(4 * (i + 1) + 0)] = ctx->boxes[i].x & 0xff;
buf[(4 * (i + 1) + 1)] = (ctx->boxes[i].x >> 16) & 0xff;
buf[(4 * (i + 1) + 2)] = ctx->boxes[i].y & 0xff;
buf[(4 * (i + 1) + 3)] = (ctx->boxes[i].y >> 16) & 0xff;
}
// calculate buffer length
const size_t used = 2 * (ctx->level.num_boxes + 1) * sizeof(uint16_t);
const size_t len = (used < sizeof(buf)) ? used : sizeof(buf);
const uint64_t hash = fnv1a((uint8_t*) buf, len);
fprintf(stderr, "hash = %lx, used = %zu, len = %zu\n", hash, used, len);
return hash;
}
#endif /* 0 */
uint64_t
sok_ctx_hash(
const sok_ctx_t * const ctx
) {
uint16_t buf[512] = {ctx->home.x, ctx->home.y, 0};
const size_t BUF_MASK = (sizeof(buf) / sizeof(uint16_t) - 1);
for (size_t i = 0; i < ctx->level.num_boxes; i++) {
buf[(2 * (i + 1) + 0) & BUF_MASK] = ctx->boxes[i].x;
buf[(2 * (i + 1) + 1) & BUF_MASK] = ctx->boxes[i].y;
}
// calculate buffer length
const size_t used = 2 * (ctx->level.num_boxes + 1) * sizeof(uint16_t);
const size_t len = (used < sizeof(buf)) ? used : sizeof(buf);
return fnv1a((uint8_t*) buf, len);
}
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