mirror of https://github.com/nealey/irc-bot
122 lines
2.2 KiB
C
122 lines
2.2 KiB
C
#include <stdio.h>
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#include <string.h>
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#include <stdint.h>
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#include "cdb.h"
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/*
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*
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* CDB Interface
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*
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*/
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/* Why I am using stdio.h
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* By Neale Pickett
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* November, 2012
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*
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* I am not as clever as the people who maintain libc.
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*
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* THE END
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*/
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#ifndef min
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#define min(a,b) ((a)<(b)?(a):(b))
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#endif
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static uint32_t
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hash(char *s, size_t len)
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{
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uint32_t h = 5381;
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size_t i;
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for (i = 0; i < len; i += 1) {
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h = ((h << 5) + h) ^ s[i];
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}
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return h;
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}
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static uint32_t
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read_u32le(FILE *f)
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{
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uint8_t d[4];
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fread(d, 4, 1, f);
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return ((d[0]<< 0) |
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(d[1] << 8) |
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(d[2] << 16) |
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(d[3] << 24));
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}
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void
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cdb_init(struct cdb_ctx *ctx, FILE *f)
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{
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ctx->f = f;
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ctx->key = NULL;
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}
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void
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cdb_find(struct cdb_ctx *ctx, char *key, uint32_t keylen)
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{
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ctx->hash_val = hash(key, keylen);
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ctx->key = key;
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ctx->keylen = keylen;
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/* Read pointer */
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fseek(ctx->f, (ctx->hash_val % 256) * 8, SEEK_SET);
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ctx->hash_pos = read_u32le(ctx->f);
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ctx->hash_len = read_u32le(ctx->f);
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ctx->entry = (ctx->hash_val / 256) % ctx->hash_len;
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}
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uint32_t
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cdb_next(struct cdb_ctx *ctx, char *buf, uint32_t buflen)
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{
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uint32_t hashval;
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uint32_t entry_pos;
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uint32_t klen;
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uint32_t dlen;
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for (;;) {
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fseek(ctx->f, ctx->hash_pos + (ctx->entry * 8), SEEK_SET);
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ctx->entry = (ctx->entry + 1) % ctx->hash_len;
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hashval = read_u32le(ctx->f);
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entry_pos = read_u32le(ctx->f);
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if (entry_pos == 0) {
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break;
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}
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if (hashval != ctx->hash_val) {
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continue;
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}
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fseek(ctx->f, entry_pos, SEEK_SET);
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klen = read_u32le(ctx->f);
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dlen = read_u32le(ctx->f);
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if (klen == ctx->keylen) {
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uint32_t i;
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for (i = 0; i < klen; i += 1) {
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int c = fgetc(ctx->f);
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if (c != ctx->key[i]) {
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break;
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}
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}
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if (i < klen) {
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continue;
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}
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if (buf) {
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return fread(buf, 1, min(dlen, buflen), ctx->f);
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} else {
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return dlen;
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}
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}
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}
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return 0;
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}
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