Utils: is_base64 function.

GitOrigin-RevId: 6b5d3079d812cb96d080a444e964067a79472d16

tdutils/td/utils/base64.cpp

@@ -7,8 +7,6 @@
 #include "td/utils/base64.h"
 
 #include "td/utils/common.h"
-#include "td/utils/logging.h"
-#include "td/utils/misc.h"
 #include "td/utils/Slice.h"
 #include "td/utils/Status.h"
 
@@ -25,7 +23,7 @@ string base64_encode(Slice input) {
   base64.reserve((input.size() + 2) / 3 * 4);
   for (size_t i = 0; i < input.size();) {
     size_t left = std::min(input.size() - i, static_cast<size_t>(3));
-    size_t c = input.ubegin()[i++] << 16;
+    int c = input.ubegin()[i++] << 16;
     base64 += symbols64[c >> 18];
     if (left != 1) {
       c |= input.ubegin()[i++] << 8;
@@ -49,24 +47,25 @@ string base64_encode(Slice input) {
 }
 
 static unsigned char char_to_value[256];
-static bool init_char_to_value() {
+static void init_base64_table() {
+  static bool is_inited = []() {
     std::fill(std::begin(char_to_value), std::end(char_to_value), 64);
     for (unsigned char i = 0; i < 64; i++) {
       char_to_value[static_cast<size_t>(symbols64[i])] = i;
     }
     return true;
+  }();
 }
 
 Result<string> base64_decode(Slice base64) {
-  static bool is_inited = init_char_to_value();
-  CHECK(is_inited);
+  init_base64_table();
 
   if ((base64.size() & 3) != 0) {
     return Status::Error("Wrong string length");
   }
 
   size_t padding_length = 0;
-  while (base64.size() > 0 && base64.back() == '=') {
+  while (!base64.empty() && base64.back() == '=') {
     base64.remove_suffix(1);
     padding_length++;
   }
@@ -78,7 +77,7 @@ Result<string> base64_decode(Slice base64) {
   output.reserve(((base64.size() + 3) >> 2) * 3);
   for (size_t i = 0; i < base64.size();) {
     size_t left = std::min(base64.size() - i, static_cast<size_t>(4));
-    size_t c = 0;
+    int c = 0;
     for (size_t t = 0; t < left; t++) {
       auto value = char_to_value[base64.ubegin()[i++]];
       if (value == 64) {
@@ -112,7 +111,7 @@ string base64url_encode(Slice input) {
   base64.reserve((input.size() + 2) / 3 * 4);
   for (size_t i = 0; i < input.size();) {
     size_t left = std::min(input.size() - i, static_cast<size_t>(3));
-    size_t c = input.ubegin()[i++] << 16;
+    int c = input.ubegin()[i++] << 16;
     base64 += url_symbols64[c >> 18];
     if (left != 1) {
       c |= input.ubegin()[i++] << 8;
@@ -132,20 +131,21 @@ string base64url_encode(Slice input) {
 }
 
 static unsigned char url_char_to_value[256];
-static bool init_url_char_to_value() {
+static void init_base64url_table() {
+  static bool is_inited = []() {
     std::fill(std::begin(url_char_to_value), std::end(url_char_to_value), 64);
     for (unsigned char i = 0; i < 64; i++) {
       url_char_to_value[static_cast<size_t>(url_symbols64[i])] = i;
     }
     return true;
+  }();
 }
 
 Result<string> base64url_decode(Slice base64) {
-  static bool is_inited = init_url_char_to_value();
-  CHECK(is_inited);
+  init_base64url_table();
 
   size_t padding_length = 0;
-  while (base64.size() > 0 && base64.back() == '=') {
+  while (!base64.empty() && base64.back() == '=') {
     base64.remove_suffix(1);
     padding_length++;
   }
@@ -161,7 +161,7 @@ Result<string> base64url_decode(Slice base64) {
   output.reserve(((base64.size() + 3) >> 2) * 3);
   for (size_t i = 0; i < base64.size();) {
     size_t left = std::min(base64.size() - i, static_cast<size_t>(4));
-    size_t c = 0;
+    int c = 0;
     for (size_t t = 0; t < left; t++) {
       auto value = url_char_to_value[base64.ubegin()[i++]];
       if (value == 64) {
@@ -188,12 +188,50 @@ Result<string> base64url_decode(Slice base64) {
   return output;
 }
 
-string base64_filter(Slice slice) {
+bool is_base64(Slice input) {
+  if ((input.size() & 3) != 0) {
+    return false;
+  }
+
+  size_t padding_length = 0;
+  while (!input.empty() && input.back() == '=') {
+    input.remove_suffix(1);
+    padding_length++;
+  }
+  if (padding_length >= 3) {
+    return false;
+  }
+
+  init_base64_table();
+  for (size_t i = 0; i < input.size(); i++) {
+    if (char_to_value[input.ubegin()[i]] == 64) {
+      return false;
+    }
+  }
+
+  if ((input.size() & 3) == 2) {
+    auto value = char_to_value[input.back()];
+    if ((value & 15) != 0) {
+      return false;
+    }
+  }
+  if ((input.size() & 3) == 3) {
+    auto value = char_to_value[input.back()];
+    if ((value & 3) != 0) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+string base64_filter(Slice input) {
   string res;
-  res.reserve(slice.size());
-  for (auto c : slice) {
-    if (is_alnum(c) || c == '+' || c == '/' || c == '=') {
-      res += c;
+  res.reserve(input.size());
+  init_base64_table();
+  for (size_t i = 0; i < input.size(); i++) {
+    if (char_to_value[input.ubegin()[i]] != 64 || input[i] == '=') {
+      res += input[i];
     }
   }
   return res;

tdutils/td/utils/base64.h

@@ -18,5 +18,8 @@ Result<string> base64_decode(Slice base64);
 string base64url_encode(Slice input);
 Result<string> base64url_decode(Slice base64);
 
-string base64_filter(Slice slice);
+bool is_base64(Slice input);
+
+string base64_filter(Slice input);
+
 }  // namespace td

tdutils/test/misc.cpp

@@ -115,7 +115,7 @@ TEST(Misc, errno_tls_bug) {
 }
 
 TEST(Misc, base64) {
-  for (int l = 0; l < 300000; l += l / 20 + 1) {
+  for (int l = 0; l < 300000; l += l / 20 + l / 1000 * 500 + 1) {
     for (int t = 0; t < 10; t++) {
       string s = rand_string(std::numeric_limits<char>::min(), std::numeric_limits<char>::max(), l);
       string encoded = base64url_encode(s);
@@ -139,6 +139,16 @@ TEST(Misc, base64) {
   ASSERT_TRUE(base64_encode("      /'.;.';≤.];,].',[.;/,.;/]/..;!@#!*(%?::;!%\";") ==
               "ICAgICAgLycuOy4nO+KJpC5dOyxdLicsWy47LywuOy9dLy4uOyFAIyEqKCU/"
               "Ojo7ISUiOw==");
+  ASSERT_TRUE(is_base64("dGVzdA==") == true);
+  ASSERT_TRUE(is_base64("dGVzdB==") == false);
+  ASSERT_TRUE(is_base64("dGVzdA=") == false);
+  ASSERT_TRUE(is_base64("dGVzdA") == false);
+  ASSERT_TRUE(is_base64("dGVz") == true);
+  ASSERT_TRUE(is_base64("") == true);
+  ASSERT_TRUE(is_base64("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/") == true);
+  ASSERT_TRUE(is_base64("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=") == false);
+  ASSERT_TRUE(is_base64("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-/") == false);
+  ASSERT_TRUE(is_base64("====") == false);
 }
 
 TEST(Misc, to_integer) {