Add a DJB2 string hashing function

include/akstdlib.h

@@ -5,6 +5,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdint.h>
 
 akerr_ErrorContext AKERR_NOIGNORE *aksl_fopen(char *pathname, char *mode, FILE **fp);
 akerr_ErrorContext AKERR_NOIGNORE *aksl_fread(void *ptr, size_t size, size_t nmemb, FILE *stream);
@@ -28,4 +29,6 @@ akerr_ErrorContext AKERR_NOIGNORE *aksl_atof(const char *nptr, double *dest);
 
 akerr_ErrorContext AKERR_NOIGNORE *aksl_realpath(const char *restrict path, char *restrict resolved_path);
 
+akerr_ErrorContext AKERR_NOIGNORE *aksl_strhash_djb2(char *str, size_t len, uint32_t *hashval);
+
 #endif

src/stdlib.c

@@ -4,6 +4,7 @@
 #include <errno.h>
 #include <string.h>
 #include <stdarg.h>
+#include <stdint.h>
 
 akerr_ErrorContext AKERR_NOIGNORE *aksl_malloc(size_t size, void **dst)
 {
@@ -174,3 +175,16 @@ akerr_ErrorContext AKERR_NOIGNORE *aksl_realpath(const char *restrict path, char
     FAIL_ZERO_RETURN(e, result, errno, "path=%s, dest=%s", path, resolved_path);
     SUCCEED_RETURN(e);
 }
+
+akerr_ErrorContext AKERR_NOIGNORE *aksl_strhash_djb2(char *str, size_t len, uint32_t *hashval)
+{
+    PREPARE_ERROR(e);
+    FAIL_ZERO_RETURN(e, str, AKERR_NULLPOINTER, "str");
+    FAIL_ZERO_RETURN(e, hashval, AKERR_NULLPOINTER, "hashval");
+    uint32_t h = 5381;
+    while (len--) {
+	h = ((h << 5) + h) + *str++;
+    }
+    *hashval = h;
+    SUCCEED_RETURN(e);
+}