From 9aaa7a77a03205e3e0a4b3688a896360da2526b5 Mon Sep 17 00:00:00 2001
From: Florian Albrechtskirchinger <falbrechtskirchinger@gmail.com>
Date: Mon, 3 Feb 2025 14:01:05 +0100
Subject: [PATCH] Refactor detail::random_string()

Refactor detail::random_string() to output random bytes in addition to
random alphanumeric strings, and change the interface to fill a buffer
given a char pointer and length, instead of returning a string.

Rename the new function to random_bytes().

Add an overload random_string() that implements the old behavior on top
of random_bytes().
---
 httplib.h | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/httplib.h b/httplib.h
index 097224b..1fec2fe 100644
--- a/httplib.h
+++ b/httplib.h
@@ -5132,7 +5132,7 @@ private:
   size_t buf_epos_ = 0;
 };
 
-inline std::string random_string(size_t length) {
+inline void random_bytes(char *ptr, size_t length, bool alphanum) {
   static const char data[] =
       "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
 
@@ -5147,11 +5147,26 @@ inline std::string random_string(size_t length) {
 
   static std::mt19937 engine(seed_sequence);
 
-  std::string result;
-  for (size_t i = 0; i < length; i++) {
-    result += data[engine() % (sizeof(data) - 1)];
+  if (alphanum) {
+    for (size_t i = 0; i < length; i++) {
+      *(ptr++) = data[engine() % (sizeof(data) - 1)];
+    }
+  } else {
+    for (size_t i = 0; i < length;) {
+      auto val = engine();
+      for (size_t j = 0; i < length && j < sizeof(val); ++i, ++j) {
+        *(ptr++) = static_cast<char>(val);
+        val >>= 8;
+      }
+    }
   }
-  return result;
+}
+
+inline std::string random_string(size_t length) {
+  std::string s;
+  s.resize(length);
+  random_bytes(&s[0], length, true);
+  return s;
 }
 
 inline std::string make_multipart_data_boundary() {