Userland: Add base64 tool

Base/usr/share/man/man1/base64.md

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+## Name
+
+base64 - encode and decode to base64
+
+## Synopsis
+
+```**sh
+$ base64 [-d|--decode] [file]
+```
+
+## Description
+
+`base64` encodes or decodes to base64 the data in file `file` or from stdin if
+file is not specified or file is `-`.
+
+## Options
+
+* `-d|--decode`: Decode data
+
+## Examples
+
+```sh
+# base64 encode the text 'foo'
+$ echo 'A' | base64
+# base64 encode the content of foo.txt
+$ base64 hi.txt
+# base64 decode the text 'Zm9v'
+$ echo 'Zm9v' | base64 -d
+# base64 decode the content of foo.txt
+$ base64 -d foo.txt
+```

Userland/base64.cpp

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+/*
+ * Copyright (c) 2020, Tom Lebreux <tomlebreux@hotmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Base64.h>
+#include <AK/ByteBuffer.h>
+#include <AK/String.h>
+#include <LibCore/ArgsParser.h>
+#include <LibCore/File.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main(int argc, char** argv)
+{
+    if (pledge("stdio rpath", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
+    bool decode = false;
+    const char* filepath = nullptr;
+
+    Core::ArgsParser args_parser;
+    args_parser.add_option(decode, "Decode data", "decode", 'd');
+    args_parser.add_positional_argument(filepath, "", "file", Core::ArgsParser::Required::No);
+    args_parser.parse(argc, argv);
+
+    ByteBuffer buffer;
+    if (filepath == nullptr || strcmp(filepath, "-") == 0) {
+        auto file = Core::File::construct();
+        bool success = file->open(
+            STDIN_FILENO,
+            Core::IODevice::OpenMode::ReadOnly,
+            Core::File::ShouldCloseFileDescription::Yes);
+        ASSERT(success);
+        buffer = file->read_all();
+    } else {
+        auto result = Core::File::open(filepath, Core::IODevice::OpenMode::ReadOnly);
+        ASSERT(!result.is_error());
+        auto file = result.value();
+        buffer = file->read_all();
+    }
+
+    if (pledge("stdio", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
+    if (decode) {
+        auto decoded = decode_base64(StringView(buffer));
+        printf("%s\n", String::copy(decoded).characters());
+        return 0;
+    }
+
+    auto encoded = encode_base64(StringView(buffer));
+    printf("%s\n", String::copy(encoded).characters());
+}