From: Nicholas Hutchinson <nshutchinson@gmail.com>
Date: Wed, 24 Feb 2021 19:32:20 +0000 (+0000)
Subject: Fix Util::read_file truncating files if size_hint is an underestimate (#808)
X-Git-Tag: v4.2.1~27
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=577656afb5f4a0ccdebe24409fa15b2ea60a3f58;p=thirdparty%2Fccache.git

Fix Util::read_file truncating files if size_hint is an underestimate (#808)

If the size_hint passed to read_file was an underestimate, or the
platform's `stat()` implementation gives an inaccurate file size (e.g.
MinGW) then `Util::read_file()` would only issue a single `read()` call
instead of reading the entire file.

Fixes #803.
---

diff --git a/src/Util.cpp b/src/Util.cpp
index 71de5f9cd..f49708fd4 100644
--- a/src/Util.cpp
+++ b/src/Util.cpp
@@ -1180,7 +1180,7 @@ read_file(const std::string& path, size_t size_hint)
   result.resize(size_hint);
 
   while (true) {
-    if (pos > result.size()) {
+    if (pos == result.size()) {
       result.resize(2 * result.size());
     }
     const size_t max_read = result.size() - pos;
diff --git a/unittest/test_Util.cpp b/unittest/test_Util.cpp
index 56d4368f7..cb2be415c 100644
--- a/unittest/test_Util.cpp
+++ b/unittest/test_Util.cpp
@@ -820,6 +820,10 @@ TEST_CASE("Util::read_file and Util::write_file")
 #else
   CHECK(data == "carpet\n\n");
 #endif
+
+  Util::write_file("size_hint_test", std::string(8192, '\0'));
+  CHECK(Util::read_file("size_hint_test", 4096 /*size_hint*/).size() == 8192);
+
   CHECK_THROWS_WITH(Util::read_file("does/not/exist"),
                     "No such file or directory");