Bug 672448 - Allow the Accept-Language header to have quality ('q') values up to 2 decimal places. r=biesi

netwerk/protocol/http/nsHttp.h

@@ -203,8 +203,8 @@ PRTimeToSeconds(PRTime t_usec)
 
 #define NowInSeconds() PRTimeToSeconds(PR_Now())
 
-// round q-value to one decimal place; return most significant digit as uint.
-#define QVAL_TO_UINT(q) ((unsigned int) ((q + 0.05) * 10.0))
+// Round q-value to 2 decimal places; return 2 most significant digits as uint.
+#define QVAL_TO_UINT(q) ((unsigned int) ((q + 0.005) * 100.0))
 
 #define HTTP_LWS " \t"
 #define HTTP_HEADER_VALUE_SEPS HTTP_LWS ","

netwerk/protocol/http/nsHttpHandler.cpp

@@ -1221,7 +1221,7 @@ PrepareAcceptLanguages(const char *i_AcceptLanguages, nsACString &o_AcceptLangua
     if (!i_AcceptLanguages)
         return NS_OK;
 
-    uint32_t n, size, wrote;
+    uint32_t n, count_n, size, wrote;
     double q, dec;
     char *p, *p2, *token, *q_Accept, *o_Accept;
     const char *comma;
@@ -1244,7 +1244,7 @@ PrepareAcceptLanguages(const char *i_AcceptLanguages, nsACString &o_AcceptLangua
     *q_Accept = '\0';
     q = 1.0;
     dec = q / (double) n;
-    n = 0;
+    count_n = 0;
     p2 = q_Accept;
     for (token = nsCRT::strtok(o_Accept, ",", &p);
          token != (char *) 0;
@@ -1257,12 +1257,28 @@ PrepareAcceptLanguages(const char *i_AcceptLanguages, nsACString &o_AcceptLangua
             *trim = '\0';
 
         if (*token != '\0') {
-            comma = n++ != 0 ? "," : ""; // delimiter if not first item
+            comma = count_n++ != 0 ? "," : ""; // delimiter if not first item
             uint32_t u = QVAL_TO_UINT(q);
-            if (u < 10)
-                wrote = PR_snprintf(p2, available, "%s%s;q=0.%u", comma, token, u);
-            else
+
+            // Only display q-value if less than 1.00.
+            if (u < 100) {
+                const char *qval_str;
+
+                // With a small number of languages, one decimal place is enough to prevent duplicate q-values.
+                // Also, trailing zeroes do not add any information, so they can be removed.
+                if ((n < 10) || ((u % 10) == 0)) {
+                    u = (u + 5) / 10;
+                    qval_str = "%s%s;q=0.%u";
+                } else {
+                    // Values below 10 require zero padding.
+                    qval_str = "%s%s;q=0.%02u";
+                }
+
+                wrote = PR_snprintf(p2, available, qval_str, comma, token, u);
+            } else {
                 wrote = PR_snprintf(p2, available, "%s%s", comma, token);
+            }
+
             q -= dec;
             p2 += wrote;
             available -= wrote;

netwerk/test/unit/test_header_Accept-Language.js

@@ -0,0 +1,88 @@
+//
+//  HTTP Accept-Language header test
+//
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+var testpath = "/bug672448";
+
+function run_test() {
+  let intlPrefs = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefService).getBranch("intl.");
+
+  // Save old value of preference for later.
+  let oldPref = intlPrefs.getCharPref("accept_languages");
+
+  // Test different numbers of languages, to test different fractions.
+  let acceptLangTests = [
+    "qaa", // 1
+    "qaa,qab", // 2
+    "qaa,qab,qac,qad", // 4
+    "qaa,qab,qac,qad,qae,qaf,qag,qah", // 8
+    "qaa,qab,qac,qad,qae,qaf,qag,qah,qai,qaj", // 10
+    "qaa,qab,qac,qad,qae,qaf,qag,qah,qai,qaj,qak", // 11
+    "qaa,qab,qac,qad,qae,qaf,qag,qah,qai,qaj,qak,qal,qam,qan,qao,qap,qaq,qar,qas,qat,qau", // 21
+    oldPref, // Restore old value of preference (and test it).
+  ];
+
+  let acceptLangTestsNum = acceptLangTests.length;
+
+  for (let i = 0; i < acceptLangTestsNum; i++) {
+    // Set preference to test value.
+    intlPrefs.setCharPref("accept_languages", acceptLangTests[i]);
+
+    // Test value.
+    test_accepted_languages();
+  }
+}
+
+function test_accepted_languages() {
+  let channel = setupChannel(testpath);
+
+  let AcceptLanguage = channel.getRequestHeader("Accept-Language");
+
+  let acceptedLanguages = AcceptLanguage.split(",");
+
+  let acceptedLanguagesLength = acceptedLanguages.length;
+
+  for (let i = 0; i < acceptedLanguagesLength; i++) {
+    let acceptedLanguage, qualityValue;
+
+    try {
+      // The q-value must conform to the definition in HTTP/1.1 Section 3.9.
+      [_, acceptedLanguage, qualityValue] = acceptedLanguages[i].trim().match(/^([a-z0-9_-]*?)(?:;q=(1(?:\.0{0,3})?|0(?:\.[0-9]{0,3})))?$/i);
+    } catch(e) {
+      do_throw("Invalid language tag or quality value: " + e);
+    }
+
+    if (i == 0) {
+      // The first language shouldn't have a quality value.
+      do_check_eq(qualityValue, undefined);
+    } else {
+      let decimalPlaces;
+
+      // When the number of languages is small, we keep the quality value to only one decimal place.
+      // Otherwise, it can be up to two decimal places.
+      if (acceptedLanguagesLength < 10) {
+        do_check_true(qualityValue.length == 3);
+
+        decimalPlaces = 1;
+      } else {
+        do_check_true(qualityValue.length >= 3);
+        do_check_true(qualityValue.length <= 4);
+
+        decimalPlaces = 2;
+      }
+
+      // All the other languages should have an evenly-spaced quality value.
+      do_check_eq(parseFloat(qualityValue).toFixed(decimalPlaces), (1.0 - ((1 / acceptedLanguagesLength) * i)).toFixed(decimalPlaces));
+    }
+  }
+}
+
+function setupChannel(path) {
+  let ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
+  let chan = ios.newChannel("http://localhost:4444" + path, "", null);
+  chan.QueryInterface(Ci.nsIHttpChannel);
+  return chan;
+}

netwerk/test/unit/xpcshell.ini

@@ -132,6 +132,7 @@ skip-if = os == "android"
 [test_gre_resources.js]
 [test_gzipped_206.js]
 [test_head.js]
+[test_header_Accept-Language.js]
 [test_headers.js]
 [test_http_headers.js]
 [test_httpcancel.js]