Add string hash.

1 files changed, 14 insertions, 0 deletions

diff --git a/cstring/include/cstring.h b/cstring/include/cstring.h
index 75a5388..de85b43 100644
--- a/cstring/include/cstring.h
+++ b/cstring/include/cstring.h
@@ -4,6 +4,7 @@
 #include <assert.h>
 #include <bsd/string.h>
 #include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
 
 /// A fixed-size string.
@@ -99,7 +100,20 @@
     assert(written >= 0);                                                 \
     str.length = (size_t)written;                                         \
     return str;                                                           \
+  }                                                                       \
+                                                                          \
+  static inline uint64_t STRING##_hash(STRING str) {                      \
+    return cstring_hash(str.str);                                         \
+  }
+
+/// Return a hash of the given string.
+static inline uint64_t cstring_hash(const char* str) {
+  uint64_t hash = 0;
+  for (size_t i = 0; i < strlen(str); ++i) {
+    hash = (uint64_t)str[i] + (hash << 6) + (hash << 16) - hash;
   }
+  return hash;
+}
 
 DEF_STRING(sstring, 32)    // Small.
 DEF_STRING(mstring, 256)   // Medium.