Utils: Add a ByteArrayToHexString helper

src/zm_utils.cpp

@@ -116,6 +116,23 @@ std::string Join(const StringVector &values, const std::string &delim) {
   return ss.str();
 }
 
+std::string ByteArrayToHexString(nonstd::span<const uint8> bytes) {
+  static constexpr char lowercase_table[] = "0123456789abcdef";
+  std::string buf;
+  buf.resize(2 * bytes.size());
+
+  const uint8 *srcPtr = bytes.data();
+  char *dstPtr = &buf[0];
+
+  for (size_t i = 0; i < bytes.size(); ++i) {
+    uint8 c = *srcPtr++;
+    *dstPtr++ = lowercase_table[c >> 4];
+    *dstPtr++ = lowercase_table[c & 0x0f];
+  }
+
+  return buf;
+}
+
 std::string Base64Encode(const std::string &str) {
   static char base64_table[64] = {'\0'};
 

src/zm_utils.h

@@ -20,12 +20,14 @@
 #ifndef ZM_UTILS_H
 #define ZM_UTILS_H
 
+#include "zm_define.h"
 #include <algorithm>
 #include <chrono>
 #include <ctime>
 #include <functional>
 #include <map>
 #include <memory>
+#include "span.hpp"
 #include <stdexcept>
 #include <string>
 #include <sys/time.h>
@@ -67,6 +69,8 @@ std::string stringtf(const std::string &format, Args... args) {
   return std::string(buf.get(), buf.get() + size - 1); // We don't want the '\0' inside
 }
 
+std::string ByteArrayToHexString(nonstd::span<const uint8> bytes);
+
 std::string Base64Encode(const std::string &str);
 
 void TimespecDiff(timespec *start, timespec *end, timespec *diff);

tests/zm_utils.cpp

@@ -140,6 +140,18 @@ TEST_CASE("Join") {
   REQUIRE(Join({"a", "b"}, "") == "ab");
 }
 
+TEST_CASE("ByteArrayToHexString") {
+  std::vector<uint8> bytes;
+
+  REQUIRE(ByteArrayToHexString(bytes) == "");
+
+  bytes = {0x00};
+  REQUIRE(ByteArrayToHexString(bytes) == "00");
+
+  bytes = {0x00, 0x01, 0x02, 0xff};
+  REQUIRE(ByteArrayToHexString(bytes) == "000102ff");
+}
+
 TEST_CASE("Base64Encode") {
   REQUIRE(Base64Encode("") == "");
   REQUIRE(Base64Encode("f") == "Zg==");