Implement form interface

This new interface allows library users to parse
application/x-www-form-urlencoded data conveniently.

1 files changed, 193 insertions, 0 deletions

diff --git a/form.c b/form.c
new file mode 100644
index 0000000..784710b
--- /dev/null
+++ b/form.c
@@ -0,0 +1,193 @@
+#define _POSIX_C_SOURCE 200809L
+
+#include "libweb/form.h"
+#include "libweb/http.h"
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+struct pair
+{
+    char *key, *value;
+};
+
+struct form
+{
+    struct pair *pairs;
+    size_t n;
+};
+
+void form_free(struct form *const f)
+{
+    if (!f)
+        return;
+
+    for (size_t i = 0; i < f->n; i++)
+    {
+        struct pair *const p = &f->pairs[i];
+
+        free(p->key);
+        free(p->value);
+    }
+
+    free(f->pairs);
+    free(f);
+}
+
+const char *form_value(const struct form *const f, const char *const key)
+{
+    for (size_t i = 0; i < f->n; i++)
+    {
+        const struct pair *const p = &f->pairs[i];
+
+        if (!strcmp(p->key, key))
+            return p->value;
+    }
+
+    return NULL;
+}
+
+static char *alloc_form_data(const char *const s, const char **const end)
+{
+    const char *const next = strchr(s, '&');
+    char *const data = next ? strndup(s, next - s) : strdup(s);
+
+    if (!data)
+    {
+        fprintf(stderr, "%s: strndup/strdup(3): %s\n", __func__,
+            strerror(errno));
+        return NULL;
+    }
+
+    *end = next ? next + 1 : s + strlen(s);
+    return data;
+}
+
+static int append(struct form *const forms, const char **const s)
+{
+    int ret = -1;
+    const char *end;
+    char *const data = alloc_form_data(*s, &end), *enckey = NULL,
+        *encvalue = NULL, *key = NULL, *value = NULL;
+    struct pair *p;
+
+    if (!data)
+    {
+        fprintf(stderr, "%s: alloc_form_data failed\n", __func__);
+        goto end;
+    }
+
+    const char *const sep = strchr(data, '=');
+
+    if (!sep)
+    {
+        ret = 1;
+        goto end;
+    }
+    else if (!data || !*(sep + 1))
+    {
+        ret = 1;
+        goto end;
+    }
+
+    const size_t keylen = sep - data;
+
+    if (!(enckey = strndup(data, keylen)))
+    {
+        fprintf(stderr, "%s: strndup(3) enckey: %s\n",
+            __func__, strerror(errno));
+        goto end;
+    }
+    else if (!(encvalue = strdup(sep + 1)))
+    {
+        fprintf(stderr, "%s: strdup(3) encvalue: %s\n",
+            __func__, strerror(errno));
+        goto end;
+    }
+    /* HTML input forms use '+' for whitespace, rather than %20. */
+    else if ((ret = http_decode_url(enckey, true, &key)))
+    {
+        fprintf(stderr, "%s: http_decode_url enckey failed\n", __func__);
+        goto end;
+    }
+    else if ((ret = http_decode_url(encvalue, true, &value)))
+    {
+        fprintf(stderr, "%s: http_decode_url encvalue failed\n", __func__);
+        goto end;
+    }
+    else if (!(p = realloc(forms->pairs, (forms->n + 1) * sizeof *p)))
+    {
+        fprintf(stderr, "%s: realloc(3): %s\n", __func__, strerror(errno));
+        goto end;
+    }
+
+    forms->pairs = p;
+    p[forms->n++] = (const struct pair)
+    {
+        .key = key,
+        .value = value
+    };
+
+    *s = end;
+    ret = 0;
+
+end:
+    if (ret)
+    {
+        free(key);
+        free(value);
+    }
+
+    free(enckey);
+    free(encvalue);
+    free(data);
+    return ret;
+}
+
+int form_foreach(const struct form *const f, const form_iter it,
+    void *const user)
+{
+    for (size_t i = 0; i < f->n; i++)
+    {
+        const struct pair *const p = &f->pairs[i];
+        const int ret = it(p->key, p->value, user);
+
+        if (ret)
+            return ret;
+    }
+
+    return 0;
+}
+
+
+int form_alloc(const char *data, struct form **const out)
+{
+    int ret = -1;
+    struct form *const f = malloc(sizeof *f);
+
+    if (!f)
+    {
+        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
+        goto failure;
+    }
+
+    *f = (const struct form){0};
+
+    while (*data)
+        if ((ret = append(f, &data)))
+        {
+            if (ret < 0)
+                fprintf(stderr, "%s: append_form failed\n", __func__);
+
+            goto failure;
+        }
+
+    *out = f;
+    return 0;
+
+failure:
+    free(f);
+    return ret;
+}