feat: add a tflite::hexdump() for printing raw memory

Add tflite::hexdump() for printing raw memory to output streams. Copy
the output format of Python's hexdump module.

tensorflow/lite/micro/BUILD

@@ -381,6 +381,20 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "hexdump",
+    srcs = [
+        "hexdump.cc",
+    ],
+    hdrs = [
+        "hexdump.h",
+    ],
+    deps = [
+        ":span",
+        ":static_vector",
+    ],
+)
+
 cc_library(
     name = "recording_allocators",
     srcs = [
@@ -556,6 +570,17 @@ cc_test(
     ],
 )
 
+cc_test(
+    name = "hexdump_test",
+    size = "small",
+    srcs = [
+        "hexdump_test.cc",
+    ],
+    deps = [
+        ":hexdump",
+    ],
+)
+
 cc_test(
     name = "memory_helpers_test",
     srcs = [

tensorflow/lite/micro/hexdump.cc

@@ -0,0 +1,66 @@
+/* Copyright 2024 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#include "tensorflow/lite/micro/hexdump.h"
+
+#include <iomanip>
+#include <iostream>
+#include <ostream>
+
+#include "tensorflow/lite/micro/static_vector.h"
+
+void tflite::hexdump(tflite::Span<const std::byte> region, std::ostream& out) {
+  auto initial_flags = out.flags();
+  out << std::hex << std::uppercase << std::setfill('0');
+
+  std::size_t byte = 0;
+  constexpr int per_line = 16;
+  const int lines = (region.size() + per_line - 1) / per_line;  // rounded up
+  for (int line = 0; line < lines; ++line) {
+    tflite::StaticVector<char, per_line> ascii;
+
+    // print address
+    out << std::setw(8) << line << ":";
+
+    for (int pos = 0; pos < per_line; ++pos) {
+      if (byte < region.size()) {
+        // print byte
+        int as_int = static_cast<int>(region[byte++]);
+        out << ' ' << std::setw(2) << as_int;
+
+        // buffer an ascii printable value
+        char c{'.'};
+        if (std::isprint(as_int)) {
+          c = static_cast<char>(as_int);
+        }
+        ascii.push_back(c);
+      } else {
+        out << "   ";
+      }
+
+      // extra space in the middle
+      if (pos == per_line / 2 - 1) {
+        out << " ";
+      }
+    }
+
+    out << "  ";
+    for (const auto& c : ascii) {
+      out << c;
+    }
+    out << '\n';
+  }
+
+  out.flags(initial_flags);
+}

tensorflow/lite/micro/hexdump.h

@@ -0,0 +1,32 @@
+/* Copyright 2024 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+// A hexdump with an output style matching Python's hexdump module.
+
+#ifndef TENSORFLOW_LITE_MICRO_HEXDUMP_H_
+#define TENSORFLOW_LITE_MICRO_HEXDUMP_H_
+
+#include <cstddef>
+#include <iostream>
+#include <ostream>
+
+#include "tensorflow/lite/micro/span.h"
+
+namespace tflite {
+
+void hexdump(Span<const std::byte> region, std::ostream& = std::cout);
+
+}  // end namespace tflite
+
+#endif  // TENSORFLOW_LITE_MICRO_HEXDUMP_H_

tensorflow/lite/micro/hexdump_test.cc

@@ -0,0 +1,9 @@
+#include "tensorflow/lite/micro/hexdump.h"
+
+#include <string>
+
+int main(int argc, char* argv[]) {
+  const std::string s{"This is a really long test string."};
+  tflite::hexdump({reinterpret_cast<const std::byte*>(s.data()), s.size()});
+  return 0;
+}