3 files changed, 86 insertions, 5 deletions
diff --git a/src/string.c b/src/string.c
index be96c63..9328911 100644
--- a/src/string.c
+++ b/src/string.c
@@ -18,8 +18,31 @@ strng_t *strng_new(smrt_arena_t *arena, u64 size) {
 strng_t *strng_from(smrt_arena_t *arena, char *c) {
     u64 size = strlen(c);
 
-    return strng_new(arena, size);
+    strng_t *s = strng_new(arena, size);
+
+    if (!s) {
+        return NULL;
+    }
+
+    memcpy((u8*)s+STRNG_BASE_POS, c, size);
+    s->len = size;
+
+    return s;
 }
 
-    b32   strng_set(strng_t *string, char *c);
-   void strng_clear(strng_t *string);
+b32 strng_set(strng_t *string, char *c) {
+    u64 size = strlen(c);
+
+    if (string->alloc_size < size) {
+        return false;
+    }
+
+    memcpy((u8*)string+STRNG_BASE_POS, c, size);
+    string->len = size;
+
+    return true;
+}
+
+void strng_clear(strng_t *string) {
+    string->len = 0;
+}
diff --git a/src/string.h b/src/string.h
index 1b5f136..b8554ff 100644
--- a/src/string.h
+++ b/src/string.h
@@ -3,7 +3,7 @@
 #include "common.h"
 #include "smrt_arena.h"
 
-#define STRNG_BASE_POS (sizeof(ez_arena_t))
+#define STRNG_BASE_POS (sizeof(strng_t))
 
 typedef struct {
     u64 alloc_size;
@@ -15,4 +15,4 @@ strng_t *strng_from(smrt_arena_t *arena, char *c);
     b32   strng_set(strng_t *string, char *c);
    void strng_clear(strng_t *string);
 
-#define STRNG_FMT(s) (int)s->len, (s+STRNG_BASE_POS)
+#define STRNG_FMT(s) (int)s->len, (char *)((u8*)s+STRNG_BASE_POS)
diff --git a/tests/string.c b/tests/string.c
new file mode 100644
index 0000000..0e78168
--- /dev/null
+++ b/tests/string.c
@@ -0,0 +1,58 @@
+#include "../src/string.h"
+
+#include <stddef.h>
+#include <stdio.h>
+
+#include <criterion/criterion.h>
+#include <criterion/internal/assert.h>
+#include <criterion/internal/test.h>
+#include <string.h>
+
+Test(string, create_string) {
+    smrt_arena_t *arena = smrt_arena_create(KiB(4), KiB(4), false);
+    strng_t *s = strng_new(arena, 50);
+
+    cr_expect(s->alloc_size == 50);
+    cr_expect(s->len == 0);
+
+    smrt_arena_destroy(arena);
+}
+
+Test(string, from_cstring) {
+    smrt_arena_t *arena = smrt_arena_create(KiB(4), KiB(4), false);
+    strng_t *s = strng_from(arena, "Hello, world.");
+
+    cr_expect(s->alloc_size == 13);
+    cr_expect(s->len == 13);
+    cr_expect(*((u8*)s+STRNG_BASE_POS) == 72);
+    cr_expect(*((u8*)s+STRNG_BASE_POS+s->len-1) == 46);
+
+    smrt_arena_destroy(arena);
+}
+
+Test(string, set_string) {
+    smrt_arena_t *arena = smrt_arena_create(KiB(4), KiB(4), false);
+    strng_t *s = strng_from(arena, "Hello, world.");
+
+    strng_set(s, "Look ma!");
+
+    cr_expect(s->alloc_size == 13);
+    cr_expect(s->len == 8);
+    cr_expect(*((u8*)s+STRNG_BASE_POS) == 76);
+    cr_expect(*((u8*)s+STRNG_BASE_POS+s->len-1) == 33);
+
+    smrt_arena_destroy(arena);
+}
+
+Test(string, format_and_copy_string) {
+    smrt_arena_t *arena = smrt_arena_create(KiB(4), KiB(4), false);
+
+    strng_t *s = strng_from(arena, "Hello, world.");
+    char *buffer = SMRTA_ALLOC_ARRAY(arena, char, s->len+1);
+
+    u64 copied = snprintf(buffer, s->len+1, "%.*s", STRNG_FMT(s));
+    cr_expect(copied == 13);
+    cr_expect(strcmp(buffer, "Hello, world.") == 0);
+
+    smrt_arena_destroy(arena);
+}