Add nascent infobot program

infobot.c

@@ -0,0 +1,142 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+/* Why I am using stdio.h
+ * By Neale Pickett
+ * November, 2012
+ *
+ * I am not as clever as the people who maintain libc.
+ *
+ * THE END
+ */
+
+/* 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)
+
+
+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;
+    }
+}
+
+int
+lookup(FILE *f, char *key)
+{
+    size_t keylen = strlen(key);
+    uint32_t h = hash(key, keylen);
+    uint32_t p, plen;
+    uint32_t i;
+
+    /* Read pointer */
+    fseek(f, (h % 256) * 8, SEEK_SET);
+    p = read_u32(f);
+    plen = read_u32(f);
+
+    /* Read hash table entries */
+    for (i = (h / 256) % plen; i < plen; i += 1) {
+        uint32_t hashval;
+        uint32_t entry_pos;
+        uint32_t klen;
+        uint32_t dlen;
+
+        fseek(f, p + (i * 8), SEEK_SET);
+        hashval = read_u32(f);
+        entry_pos = read_u32(f);
+        if (entry_pos == 0) {
+            break;
+        }
+        if (hashval != h) {
+            continue;
+        }
+
+        fseek(f, entry_pos, SEEK_SET);
+        klen = read_u32(f);
+        dlen = read_u32(f);
+
+        if (klen == keylen) {
+            uint32_t i;
+
+            for (i = 0; i < klen; i += 1) {
+                int c = fgetc(f);
+
+                if (c != key[i]) {
+                    break;
+                }
+            }
+
+            if (i < klen) {
+                continue;
+            }
+
+            for (i = 0; i < dlen; i += 1) {
+                int c = fgetc(f);
+
+                putchar(c);
+            }
+        }
+    }
+
+    return 0;
+}
+
+
+
+int
+main(int argc, char *argv[])
+{
+    if (1 == argc) {
+        return usage();
+    }
+
+    return lookup(stdin, argv[1]);
+}