util/formatted_output.h: hex-dump utility

Adds Genode::Hex_dump class to the formatted_output.h header. This class can be
used to print a hexadecimal dump of a byte range. The data is printed in a
format similar to that used by Linux's 'xxd'. In addition to the 'xxd' format,
consecutive duplicate lines are replaced with a single "*\n" as done also by
Linux's 'hexdump'.

Ref #4966

repos/os/include/util/formatted_output.h

@@ -15,6 +15,7 @@
 #define _INCLUDE__OS__UTIL__FORMATTED_OUTPUT_H_
 
 #include <base/output.h>
+#include <util/string.h>
 
 namespace Genode {
 
@@ -23,6 +24,8 @@ namespace Genode {
 	template <typename> struct Left_aligned;
 	template <typename> struct Right_aligned;
 
+	class Hex_dump;
+
 	/**
 	 * Return the number of characters needed when rendering 'args' as text
 	 */
@@ -119,4 +122,93 @@ struct Genode::Right_aligned
 	}
 };
 
+
+class Genode::Hex_dump
+{
+	private:
+
+		static constexpr size_t _max_bytes_per_line { 16 };
+		uint8_t const * const _base;
+		size_t const _size;
+		size_t const _num_lines { (_size + _max_bytes_per_line - 1) / _max_bytes_per_line };
+
+		static bool _printable_ascii(char c)
+		{
+			return c > 31 && c < 127;
+		}
+
+		static void _print_line_as_hex_words(Output &out, uint8_t const *base, size_t size)
+		{
+			using Genode::print;
+			static constexpr size_t max_bytes_per_word { 2 };
+			for (size_t idx { 0 }; idx < _max_bytes_per_line; idx++) {
+
+				if (idx && idx % max_bytes_per_word == 0)
+					print(out, " ");
+
+				if (idx < size)
+					print(out, Hex(base[idx], Hex::OMIT_PREFIX, Hex::PAD));
+				else
+					print(out, "  ");
+			}
+		}
+
+		static void _print_line_as_ascii(Output &out, uint8_t const *base, size_t size)
+		{
+			using Genode::print;
+			for (size_t idx { 0 }; idx < size; idx++) {
+
+				char const *char_ptr { (char *)&base[idx] };
+				if (_printable_ascii(*char_ptr))
+					print(out, Cstring { char_ptr, 1 });
+				else
+					print(out, ".");
+			}
+		}
+
+		static void _print_line_offset(Output &out, size_t line_offset)
+		{
+			Genode::print(out, Hex((uint32_t)line_offset, Hex::OMIT_PREFIX, Hex::PAD));
+		}
+
+	public:
+
+		Hex_dump(auto const &range)
+		: _base { (uint8_t *)range.start }, _size { range.num_bytes } { }
+
+		void print(Output &out) const
+		{
+			using Genode::print;
+			uint8_t const *prev_line_ptr { nullptr };
+			bool prev_line_was_duplicate { false };
+			for (size_t line_idx { 0 }; line_idx < _num_lines; line_idx++) {
+
+				size_t const line_offset { line_idx * _max_bytes_per_line };
+				size_t const line_size { min((size_t)_max_bytes_per_line, _size - line_offset) };
+				uint8_t const *line_ptr { &_base[line_offset] };
+				bool const last_line { line_idx == _num_lines - 1 };
+
+				bool line_is_duplicate { false };
+				if (prev_line_ptr)
+					line_is_duplicate = !memcmp(prev_line_ptr, line_ptr, line_size);
+
+				if (!line_is_duplicate || last_line) {
+
+					_print_line_offset(out, line_offset);
+					print(out, ": ");
+					_print_line_as_hex_words(out, line_ptr, line_size);
+					print(out, "  ");
+					_print_line_as_ascii(out, line_ptr, line_size);
+					print(out, last_line ? "" : "\n");
+				}
+				if (line_is_duplicate && !prev_line_was_duplicate && !last_line)
+					print(out, "*\n");
+
+
+				prev_line_ptr = line_ptr;
+				prev_line_was_duplicate = line_is_duplicate;
+			}
+		}
+};
+
 #endif /* _INCLUDE__OS__UTIL__FORMATTED_OUTPUT_H_ */