From 2cb9b191b66a69aba15ebdefe8cd4bdd962e5b2b Mon Sep 17 00:00:00 2001
From: Dirk Engling <erdgeist@erdgeist.org>
Date: Sat, 24 Oct 2026 05:49:51 +0200
Subject: Add tests for the url escaper

---
 tests/t_scan_urlencoded_query.c | 107 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)

diff --git a/tests/t_scan_urlencoded_query.c b/tests/t_scan_urlencoded_query.c
index 4c1ef23..6fa34e0 100644
--- a/tests/t_scan_urlencoded_query.c
+++ b/tests/t_scan_urlencoded_query.c
@@ -254,6 +254,106 @@ static void case_fixed_int_bounded(void) {
   CHECK_INT(value, 123);
 }
 
+
+/* The encoding direction. Which bytes survive unescaped is fixed by what
+   existing parsers of the urlencoded full scrape expect, so these cases pin
+   the set rather than describe a preference. */
+
+static void case_fmt_passes_safe_bytes(void) {
+  const uint8_t src[] = "aZ09$-./=_~";
+  char          dest[64];
+  size_t        n;
+
+  test_case("alphanumerics and the safe punctuation pass through");
+  n       = fmt_urlencoded(dest, src, 11);
+  dest[n] = 0;
+  CHECK_INT(n, 11);
+  CHECK_STR(dest, "aZ09$-./=_~");
+}
+
+static void case_fmt_escapes_the_rest(void) {
+  const uint8_t src[] = {' ', '%', '&', '+', ':', '?'};
+  char          dest[64];
+  size_t        n;
+
+  test_case("everything else becomes a percent escape");
+  n       = fmt_urlencoded(dest, src, sizeof(src));
+  dest[n] = 0;
+  CHECK_INT(n, 18);
+  CHECK_STR(dest, "%20%25%26%2b%3a%3f");
+}
+
+static void case_fmt_hex_is_lower_case(void) {
+  const uint8_t src[] = {0x00, 0xab, 0xff};
+  char          dest[64];
+  size_t        n;
+
+  test_case("escapes use lower case hex digits");
+  n       = fmt_urlencoded(dest, src, sizeof(src));
+  dest[n] = 0;
+  CHECK_INT(n, 9);
+  CHECK_STR(dest, "%00%ab%ff");
+}
+
+static void case_fmt_length_only(void) {
+  const uint8_t src[] = {'a', 0xff, 'b'};
+
+  test_case("a null destination reports the length without writing");
+  CHECK_INT(fmt_urlencoded(NULL, src, sizeof(src)), 5);
+  CHECK_INT(fmt_urlencoded(NULL, src, 0), 0);
+}
+
+static void case_fmt_zero_length(void) {
+  char dest[4];
+
+  test_case("a zero length input writes nothing");
+  memset(dest, 0x5a, sizeof(dest));
+  CHECK_INT(fmt_urlencoded(dest, (const uint8_t *)"abc", 0), 0);
+  CHECK_MEM(dest, "\x5a\x5a\x5a\x5a", 4);
+}
+
+static void case_fmt_worst_case_fits(void) {
+  uint8_t src[20];
+  char    dest[61];
+  size_t  i, n;
+
+  test_case("a hash of entirely unsafe bytes needs three times its length");
+  for (i = 0; i < sizeof(src); ++i)
+    src[i] = 0xff;
+  n       = fmt_urlencoded(dest, src, sizeof(src));
+  dest[n] = 0;
+  CHECK_INT(n, 60);
+  for (i = 0; i < 20; ++i)
+    if (memcmp(dest + 3 * i, "%ff", 3)) {
+      test_failf(__FILE__, __LINE__, "escape %zu is wrong", i);
+      return;
+    }
+  ++test_checks;
+}
+
+static void case_fmt_decoder_disagrees_on_dollar(void) {
+  /* Documenting a known asymmetry rather than a wish. Of the bytes the
+     encoder passes through unescaped, '$' is the only one the decoder then
+     refuses, and it refuses the whole string rather than stopping short.
+     Output of the urlencoded full scrape therefore does not round trip
+     through scan_urlencoded_query when a hash contains 0x24. Harmless today
+     because only third party tooling reads that output. */
+  const uint8_t src[]  = {'a', '$', 'b'};
+  char          dest[16];
+  char          scanned[16];
+  char         *p = dest;
+  size_t        n;
+  ssize_t       got;
+
+  test_case("the encoder passes '$' but the decoder rejects it");
+  n       = fmt_urlencoded(dest, src, sizeof(src));
+  dest[n] = 0;
+  CHECK_STR(dest, "a$b");
+
+  got = scan_urlencoded_query(&p, scanned, SCAN_SEARCHPATH_VALUE);
+  CHECK_INT(got, -1);
+}
+
 void test_scan_urlencoded_query(void) {
   case_path();
   case_param_and_value();
@@ -271,4 +371,11 @@ void test_scan_urlencoded_query(void) {
   case_find_keywords();
   case_fixed_int();
   case_fixed_int_bounded();
+  case_fmt_passes_safe_bytes();
+  case_fmt_escapes_the_rest();
+  case_fmt_hex_is_lower_case();
+  case_fmt_length_only();
+  case_fmt_zero_length();
+  case_fmt_worst_case_fits();
+  case_fmt_decoder_disagrees_on_dollar();
 }
-- 
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