1 files changed, 148 insertions, 0 deletions
diff --git a/src/subst.c b/src/subst.c
new file mode 100644
index 0000000..6c8bec6
--- /dev/null
+++ b/src/subst.c
@@ -0,0 +1,148 @@
+#include "l2su.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+struct l2_subst__item {
+  char *name;
+  char *value;
+
+  struct l2_subst__item *next;
+};
+
+struct l2_subst {
+  struct l2_subst__item *items;
+  int status;
+};
+
+int l2_subst_init(l2_subst_t **sp)
+{
+  l2_subst_t *ret = calloc(1, sizeof(struct l2_subst));
+  if (!ret) return -1;
+
+  *sp = ret;
+
+  ret->items = NULL;
+  ret->status = 0;
+
+  return 0;
+}
+
+int l2_subst_add(l2_subst_t *sp, const char *name, const char *value)
+{
+  if (sp->status < 0) return sp->status;
+
+  char *namedup = strdup(name);
+  char *valdup = strdup(value);
+  struct l2_subst__item *item = calloc(1, sizeof(struct l2_subst__item));
+
+  if (!namedup || !valdup || !item) {
+    free(namedup);
+    free(valdup);
+    free(item);
+    sp->status = -1;
+    return -1;
+  }
+
+  item->name = namedup;
+  item->value = valdup;
+  item->next = sp->items;
+  sp->items = item;
+
+  return 0;
+}
+
+const char *l2_subst__find(l2_subst_t *sp, const char *name, size_t len)
+{
+  for (struct l2_subst__item *item = sp->items; item; item = item->next) {
+    if (!strncmp(item->name, name, len)) return item->value;
+  }
+  return NULL;
+}
+
+int l2_subst__append(char **retbuf, size_t *sz, size_t *cap, const char *start, const char *end)
+{
+  ptrdiff_t len = end - start;
+  if (len <= 0) return 0;
+
+  if (*sz + len > *cap) {
+    size_t newcap = *cap ? *cap : 16;
+    while (newcap && *sz + len > newcap) newcap <<= 1;
+
+    if (!newcap) {
+      goto cleanup;
+    }
+
+    char *newbuf = realloc(*retbuf, newcap);
+    if (!newbuf) {
+      goto cleanup;
+    }
+
+    *retbuf = newbuf;
+    *cap = newcap;
+  }
+
+  memcpy(*retbuf + *sz, start, len);
+  *sz += len;
+  return 0;
+
+cleanup:
+  free(*retbuf);
+  return -1;
+}
+
+int l2_subst_apply(l2_subst_t *sp, const char *in, char **out)
+{
+  if (sp->status < 0) return sp->status;
+
+  char *retbuf = NULL, *temp;
+  size_t size = 0;
+  size_t cap = 0;
+
+  const char *lastcpy = in;
+  const char *open = NULL;
+  const char *cur;
+
+  for (cur = in; *cur; ++cur) {
+    if (*cur == '$' && *(cur + 1) == '{') {
+      if (l2_subst__append(&retbuf, &size, &cap, lastcpy, cur) < 0)
+       return -1;
+
+      lastcpy = cur;
+      open = cur + 2;
+      continue;
+    } else if (*cur == '}' && open) {
+      const char *rep = l2_subst__find(sp, open, cur - open);
+      if (rep) {
+        if (l2_subst__append(&retbuf, &size, &cap, rep, rep + strlen(rep)) < 0)
+          return -1;
+        lastcpy = cur + 1;
+      }
+
+      open = NULL;
+    }
+  }
+
+  if (l2_subst__append(&retbuf, &size, &cap, lastcpy, cur + 1) < 0) return -1;
+
+  temp = realloc(retbuf, size);
+  if (temp) retbuf = temp;
+  *out = retbuf;
+
+  return 0;
+}
+
+void l2_subst_free(l2_subst_t *sp)
+{
+  if (!sp) return;
+
+  for (struct l2_subst__item *cur = sp->items, *temp; cur; cur = temp) {
+    temp = cur->next;
+    free(cur->name);
+    free(cur->value);
+    free(cur);
+  }
+
+  free(sp);
+  return;
+}