cdb reader, for C infobot

cdb.c

@@ -0,0 +1,155 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include "cdb.h"
+
+/* Some things I use for debugging */
+#ifdef NODUMP
+#  define DUMPf(fmt, args...)
+#else
+#  define DUMPf(fmt, args...) fprintf(stderr, "%s:%s:%d " fmt "\n", __FILE__, __FUNCTION__, __LINE__, ##args)
+#endif
+#define DUMP() DUMPf("")
+#define DUMP_u(v) DUMPf("%s = %u", #v, v)
+#define DUMP_d(v) DUMPf("%s = %d", #v, v)
+#define DUMP_x(v) DUMPf("%s = 0x%x", #v, v)
+#define DUMP_s(v) DUMPf("%s = %s", #v, v)
+#define DUMP_c(v) DUMPf("%s = %c", #v, v)
+#define DUMP_p(v) DUMPf("%s = %p", #v, v)
+
+#ifndef min
+#define min(a,b) ((a)<(b)?(a):(b))
+#endif
+
+uint32_t
+hash(char *s, size_t len)
+{
+    uint32_t h = 5381;
+    size_t i;
+
+    for (i = 0; i < len; i += 1) {
+        h = ((h << 5) + h) ^ s[i];
+    }
+    return h;
+}
+
+int
+usage()
+{
+    fprintf(stderr, "Usage: infobot\n");
+
+    return 0;
+}
+
+uint32_t
+read_u32(FILE *f)
+{
+    uint8_t d[4];
+
+    fread(d, 4, 1, f);
+    return ((d[0]<< 0) |
+            (d[1] << 8) |
+            (d[2] << 16) |
+            (d[3] << 24));
+}
+
+
+int
+bufcmp(char *a, size_t alen, char *b, size_t blen)
+{
+    if (alen == blen) {
+        return memcmp(a, b, blen);
+    } else {
+        return alen - blen;
+    }
+}
+
+void
+cdb_init(struct cdb_ctx *ctx, FILE *f)
+{
+    ctx->f = f;
+    ctx->key = NULL;
+}
+
+void
+cdb_find(struct cdb_ctx *ctx, char *key, uint32_t keylen)
+{
+    ctx->hash_val = hash(key, keylen);
+
+    ctx->key = key;
+    ctx->keylen = keylen;
+
+    /* Read pointer */
+    fseek(ctx->f, (ctx->hash_val % 256) * 8, SEEK_SET);
+    ctx->hash_pos = read_u32(ctx->f);
+    ctx->hash_len = read_u32(ctx->f);
+    ctx->entry = (ctx->hash_val / 256) % ctx->hash_len;
+}
+
+uint32_t
+cdb_next(struct cdb_ctx *ctx, char *buf, uint32_t buflen)
+{
+    uint32_t hashval;
+    uint32_t entry_pos;
+    uint32_t klen;
+    uint32_t dlen;
+
+    for (;;) {
+        fseek(ctx->f, ctx->hash_pos + (ctx->entry++ * 8), SEEK_SET);
+        hashval = read_u32(ctx->f);
+        entry_pos = read_u32(ctx->f);
+        if (entry_pos == 0) {
+            break;
+        }
+        if (hashval != ctx->hash_val) {
+            continue;
+        }
+
+        fseek(ctx->f, entry_pos, SEEK_SET);
+        klen = read_u32(ctx->f);
+        dlen = read_u32(ctx->f);
+
+        if (klen == ctx->keylen) {
+            uint32_t i;
+
+            for (i = 0; i < klen; i += 1) {
+                int c = fgetc(ctx->f);
+
+                if (c != ctx->key[i]) {
+                    break;
+                }
+            }
+
+            if (i < klen) {
+                continue;
+            }
+
+            return fread(buf, 1, min(dlen, buflen), ctx->f);
+        }
+    }
+
+    return 0;
+}
+
+
+int
+main(int argc, char *argv[])
+{
+    if (1 == argc) {
+        return usage();
+    }
+
+    {
+        struct cdb_ctx ctx;
+        char buf[8192];
+        int32_t r;
+
+        cdb_init(&ctx, stdin);
+        cdb_find(&ctx, argv[1], strlen(argv[1]));
+        while ((r = cdb_next(&ctx, buf, sizeof buf))) {
+            printf("%.*s\n", r, buf);
+        }
+    }
+
+    return 0;
+}