Clean up Base* code

src/libfetchers/git-utils.cc

@@ -2,6 +2,7 @@
 #include "nix/fetchers/git-lfs-fetch.hh"
 #include "nix/fetchers/cache.hh"
 #include "nix/fetchers/fetch-settings.hh"
+#include "nix/util/base-n.hh"
 #include "nix/util/finally.hh"
 #include "nix/util/processes.hh"
 #include "nix/util/signals.hh"
@@ -608,7 +609,7 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
             // Calculate sha256 fingerprint from public key and escape the regex symbol '+' to match the key literally
             std::string keyDecoded;
             try {
-                keyDecoded = base64Decode(k.key);
+                keyDecoded = base64::decode(k.key);
             } catch (Error & e) {
                 e.addTrace({}, "while decoding public key '%s' used for git signature", k.key);
             }

src/libstore/machines.cc

@@ -1,3 +1,4 @@
+#include "nix/util/base-n.hh"
 #include "nix/store/machines.hh"
 #include "nix/store/globals.hh"
 #include "nix/store/store-open.hh"
@@ -158,7 +159,7 @@ static Machine parseBuilderLine(const StringSet & defaultSystems, const std::str
     auto ensureBase64 = [&](size_t fieldIndex) {
         const auto & str = tokens[fieldIndex];
         try {
-            base64Decode(str);
+            base64::decode(str);
         } catch (FormatError & e) {
             e.addTrace({}, "while parsing machine specification at a column #%lu in a row: '%s'", fieldIndex, line);
             throw;

src/libstore/ssh.cc

@@ -4,13 +4,14 @@
 #include "nix/util/environment-variables.hh"
 #include "nix/util/util.hh"
 #include "nix/util/exec.hh"
+#include "nix/util/base-n.hh"
 
 namespace nix {
 
 static std::string parsePublicHostKey(std::string_view host, std::string_view sshPublicHostKey)
 {
     try {
-        return base64Decode(sshPublicHostKey);
+        return base64::decode(sshPublicHostKey);
     } catch (Error & e) {
         e.addTrace({}, "while decoding ssh public host key for host '%s'", host);
         throw;

src/libutil-tests/base-n.cc

@@ -0,0 +1,68 @@
+#include <gtest/gtest.h>
+#include <numeric>
+
+#include "nix/util/base-n.hh"
+#include "nix/util/error.hh"
+
+namespace nix {
+
+static const std::span<const std::byte> stringToByteSpan(const std::string_view s)
+{
+    return {(const std::byte *) s.data(), s.size()};
+}
+
+/* ----------------------------------------------------------------------------
+ * base64::encode
+ * --------------------------------------------------------------------------*/
+
+TEST(base64Encode, emptyString)
+{
+    ASSERT_EQ(base64::encode(stringToByteSpan("")), "");
+}
+
+TEST(base64Encode, encodesAString)
+{
+    ASSERT_EQ(base64::encode(stringToByteSpan("quod erat demonstrandum")), "cXVvZCBlcmF0IGRlbW9uc3RyYW5kdW0=");
+}
+
+TEST(base64Encode, encodeAndDecode)
+{
+    auto s = "quod erat demonstrandum";
+    auto encoded = base64::encode(stringToByteSpan(s));
+    auto decoded = base64::decode(encoded);
+
+    ASSERT_EQ(decoded, s);
+}
+
+TEST(base64Encode, encodeAndDecodeNonPrintable)
+{
+    char s[256];
+    std::iota(std::rbegin(s), std::rend(s), 0);
+
+    auto encoded = base64::encode(std::as_bytes(std::span<const char>{std::string_view{s}}));
+    auto decoded = base64::decode(encoded);
+
+    EXPECT_EQ(decoded.length(), 255u);
+    ASSERT_EQ(decoded, s);
+}
+
+/* ----------------------------------------------------------------------------
+ * base64::decode
+ * --------------------------------------------------------------------------*/
+
+TEST(base64Decode, emptyString)
+{
+    ASSERT_EQ(base64::decode(""), "");
+}
+
+TEST(base64Decode, decodeAString)
+{
+    ASSERT_EQ(base64::decode("cXVvZCBlcmF0IGRlbW9uc3RyYW5kdW0="), "quod erat demonstrandum");
+}
+
+TEST(base64Decode, decodeThrowsOnInvalidChar)
+{
+    ASSERT_THROW(base64::decode("cXVvZCBlcm_0IGRlbW9uc3RyYW5kdW0="), Error);
+}
+
+} // namespace nix

src/libutil-tests/meson.build

@@ -44,6 +44,7 @@ subdir('nix-meson-build-support/common')
 
 sources = files(
   'args.cc',
+  'base-n.cc',
   'canon-path.cc',
   'checked-arithmetic.cc',
   'chunked-vector.cc',

src/libutil-tests/util.cc

@@ -3,6 +3,7 @@
 #include "nix/util/file-system.hh"
 #include "nix/util/terminal.hh"
 #include "nix/util/strings.hh"
+#include "nix/util/base-n.hh"
 
 #include <limits.h>
 #include <gtest/gtest.h>
@@ -48,60 +49,6 @@ TEST(hasSuffix, trivialCase)
     ASSERT_TRUE(hasSuffix("foobar", "bar"));
 }
 
-/* ----------------------------------------------------------------------------
- * base64Encode
- * --------------------------------------------------------------------------*/
-
-TEST(base64Encode, emptyString)
-{
-    ASSERT_EQ(base64Encode(""), "");
-}
-
-TEST(base64Encode, encodesAString)
-{
-    ASSERT_EQ(base64Encode("quod erat demonstrandum"), "cXVvZCBlcmF0IGRlbW9uc3RyYW5kdW0=");
-}
-
-TEST(base64Encode, encodeAndDecode)
-{
-    auto s = "quod erat demonstrandum";
-    auto encoded = base64Encode(s);
-    auto decoded = base64Decode(encoded);
-
-    ASSERT_EQ(decoded, s);
-}
-
-TEST(base64Encode, encodeAndDecodeNonPrintable)
-{
-    char s[256];
-    std::iota(std::rbegin(s), std::rend(s), 0);
-
-    auto encoded = base64Encode(s);
-    auto decoded = base64Decode(encoded);
-
-    EXPECT_EQ(decoded.length(), 255u);
-    ASSERT_EQ(decoded, s);
-}
-
-/* ----------------------------------------------------------------------------
- * base64Decode
- * --------------------------------------------------------------------------*/
-
-TEST(base64Decode, emptyString)
-{
-    ASSERT_EQ(base64Decode(""), "");
-}
-
-TEST(base64Decode, decodeAString)
-{
-    ASSERT_EQ(base64Decode("cXVvZCBlcmF0IGRlbW9uc3RyYW5kdW0="), "quod erat demonstrandum");
-}
-
-TEST(base64Decode, decodeThrowsOnInvalidChar)
-{
-    ASSERT_THROW(base64Decode("cXVvZCBlcm_0IGRlbW9uc3RyYW5kdW0="), Error);
-}
-
 /* ----------------------------------------------------------------------------
  * getLine
  * --------------------------------------------------------------------------*/

src/libutil/base-n.cc

@@ -0,0 +1,114 @@
+#include <string_view>
+
+#include "nix/util/array-from-string-literal.hh"
+#include "nix/util/util.hh"
+#include "nix/util/base-n.hh"
+
+using namespace std::literals;
+
+namespace nix {
+
+constexpr static const std::array<char, 16> base16Chars = "0123456789abcdef"_arrayNoNull;
+
+std::string base16::encode(std::span<const std::byte> b)
+{
+    std::string buf;
+    buf.reserve(b.size() * 2);
+    for (size_t i = 0; i < b.size(); i++) {
+        buf.push_back(base16Chars[(uint8_t) b.data()[i] >> 4]);
+        buf.push_back(base16Chars[(uint8_t) b.data()[i] & 0x0f]);
+    }
+    return buf;
+}
+
+std::string base16::decode(std::string_view s)
+{
+    auto parseHexDigit = [&](char c) {
+        if (c >= '0' && c <= '9')
+            return c - '0';
+        if (c >= 'A' && c <= 'F')
+            return c - 'A' + 10;
+        if (c >= 'a' && c <= 'f')
+            return c - 'a' + 10;
+        throw FormatError("invalid character in Base16 string: '%c'", c);
+    };
+
+    assert(s.size() % 2 == 0);
+    auto decodedSize = s.size() / 2;
+
+    std::string res;
+    res.reserve(decodedSize);
+
+    for (unsigned int i = 0; i < decodedSize; i++) {
+        res.push_back(parseHexDigit(s[i * 2]) << 4 | parseHexDigit(s[i * 2 + 1]));
+    }
+
+    return res;
+}
+
+constexpr static const std::array<char, 64> base64Chars =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"_arrayNoNull;
+
+std::string base64::encode(std::span<const std::byte> s)
+{
+    std::string res;
+    res.reserve((s.size() + 2) / 3 * 4);
+    int data = 0, nbits = 0;
+
+    for (std::byte c : s) {
+        data = data << 8 | (uint8_t) c;
+        nbits += 8;
+        while (nbits >= 6) {
+            nbits -= 6;
+            res.push_back(base64Chars[data >> nbits & 0x3f]);
+        }
+    }
+
+    if (nbits)
+        res.push_back(base64Chars[data << (6 - nbits) & 0x3f]);
+    while (res.size() % 4)
+        res.push_back('=');
+
+    return res;
+}
+
+std::string base64::decode(std::string_view s)
+{
+    constexpr char npos = -1;
+    constexpr std::array<char, 256> base64DecodeChars = [&] {
+        std::array<char, 256> result{};
+        for (auto & c : result)
+            c = npos;
+        for (int i = 0; i < 64; i++)
+            result[base64Chars[i]] = i;
+        return result;
+    }();
+
+    std::string res;
+    // Some sequences are missing the padding consisting of up to two '='.
+    //                    vvv
+    res.reserve((s.size() + 2) / 4 * 3);
+    unsigned int d = 0, bits = 0;
+
+    for (char c : s) {
+        if (c == '=')
+            break;
+        if (c == '\n')
+            continue;
+
+        char digit = base64DecodeChars[(unsigned char) c];
+        if (digit == npos)
+            throw FormatError("invalid character in Base64 string: '%c'", c);
+
+        bits += 6;
+        d = d << 6 | digit;
+        if (bits >= 8) {
+            res.push_back(d >> (bits - 8) & 0xff);
+            bits -= 8;
+        }
+    }
+
+    return res;
+}
+
+} // namespace nix

src/libutil/base-nix-32.cc

@@ -1,6 +1,7 @@
 #include <cassert>
 
 #include "nix/util/base-nix-32.hh"
+#include "nix/util/util.hh"
 
 namespace nix {
 
@@ -16,12 +17,12 @@ constexpr const std::array<unsigned char, 256> BaseNix32::reverseMap = [] {
     return map;
 }();
 
-std::string BaseNix32::encode(std::span<const uint8_t> originalData)
+std::string BaseNix32::encode(std::span<const std::byte> bs)
 {
-    if (originalData.size() == 0)
+    if (bs.size() == 0)
         return {};
 
-    size_t len = encodedLength(originalData.size());
+    size_t len = encodedLength(bs.size());
     assert(len);
 
     std::string s;
@@ -31,12 +32,42 @@ std::string BaseNix32::encode(std::span<const uint8_t> originalData)
         unsigned int b = n * 5;
         unsigned int i = b / 8;
         unsigned int j = b % 8;
-        unsigned char c =
-            (originalData.data()[i] >> j) | (i >= originalData.size() - 1 ? 0 : originalData.data()[i + 1] << (8 - j));
-        s.push_back(characters[c & 0x1f]);
+        std::byte c = (bs.data()[i] >> j) | (i >= bs.size() - 1 ? std::byte{0} : bs.data()[i + 1] << (8 - j));
+        s.push_back(characters[uint8_t(c & std::byte{0x1f})]);
     }
 
     return s;
 }
 
+std::string BaseNix32::decode(std::string_view s)
+{
+    std::string res;
+    res.reserve((s.size() * 5 + 7) / 8); // ceiling(size * 5/8)
+
+    for (unsigned int n = 0; n < s.size(); ++n) {
+        char c = s[s.size() - n - 1];
+        auto digit_opt = BaseNix32::lookupReverse(c);
+
+        if (!digit_opt)
+            throw FormatError("invalid character in Nix32 (Nix's Base32 variation) string: '%c'", c);
+
+        uint8_t digit = *digit_opt;
+
+        unsigned int b = n * 5;
+        unsigned int i = b / 8;
+        unsigned int j = b % 8;
+
+        // Ensure res has enough space
+        res.resize(i + 1);
+        res[i] |= digit << j;
+
+        if (digit >> (8 - j)) {
+            res.resize(i + 2);
+            res[i + 1] |= digit >> (8 - j);
+        }
+    }
+
+    return res;
+}
+
 } // namespace nix