util: extract {Read,Write}BinaryFile() to its own files

Extract `ReadBinaryFile()` and `WriteBinaryFile()` from `torcontrol.cpp`
to its own `readwritefile.{h,cpp}` files, so that it can be reused from
other modules.

src/Makefile.am

@@ -242,6 +242,7 @@ BITCOIN_CORE_H = \
   util/message.h \
   util/moneystr.h \
   util/rbf.h \
+  util/readwritefile.h \
   util/ref.h \
   util/settings.h \
   util/sock.h \
@@ -572,6 +573,7 @@ libbitcoin_util_a_SOURCES = \
   util/message.cpp \
   util/moneystr.cpp \
   util/rbf.cpp \
+  util/readwritefile.cpp \
   util/settings.cpp \
   util/threadnames.cpp \
   util/spanparsing.cpp \

src/torcontrol.cpp

@@ -12,6 +12,7 @@
 #include <net.h>
 #include <netaddress.h>
 #include <netbase.h>
+#include <util/readwritefile.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 #include <util/time.h>
@@ -362,52 +363,6 @@ std::map<std::string,std::string> ParseTorReplyMapping(const std::string &s)
     return mapping;
 }
 
-/** Read full contents of a file and return them in a std::string.
- * Returns a pair <status, string>.
- * If an error occurred, status will be false, otherwise status will be true and the data will be returned in string.
- *
- * @param maxsize Puts a maximum size limit on the file that is read. If the file is larger than this, truncated data
- *         (with len > maxsize) will be returned.
- */
-static std::pair<bool,std::string> ReadBinaryFile(const fs::path &filename, size_t maxsize=std::numeric_limits<size_t>::max())
-{
-    FILE *f = fsbridge::fopen(filename, "rb");
-    if (f == nullptr)
-        return std::make_pair(false,"");
-    std::string retval;
-    char buffer[128];
-    size_t n;
-    while ((n=fread(buffer, 1, sizeof(buffer), f)) > 0) {
-        // Check for reading errors so we don't return any data if we couldn't
-        // read the entire file (or up to maxsize)
-        if (ferror(f)) {
-            fclose(f);
-            return std::make_pair(false,"");
-        }
-        retval.append(buffer, buffer+n);
-        if (retval.size() > maxsize)
-            break;
-    }
-    fclose(f);
-    return std::make_pair(true,retval);
-}
-
-/** Write contents of std::string to a file.
- * @return true on success.
- */
-static bool WriteBinaryFile(const fs::path &filename, const std::string &data)
-{
-    FILE *f = fsbridge::fopen(filename, "wb");
-    if (f == nullptr)
-        return false;
-    if (fwrite(data.data(), 1, data.size(), f) != data.size()) {
-        fclose(f);
-        return false;
-    }
-    fclose(f);
-    return true;
-}
-
 /****** Bitcoin specific TorController implementation ********/
 
 /** Controller that connects to Tor control socket, authenticate, then create

src/util/readwritefile.cpp

@@ -0,0 +1,47 @@
+// Copyright (c) 2015-2020 The Bitcoin Core developers
+// Copyright (c) 2017 The Zcash developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <fs.h>
+
+#include <limits>
+#include <stdio.h>
+#include <string>
+#include <utility>
+
+std::pair<bool,std::string> ReadBinaryFile(const fs::path &filename, size_t maxsize=std::numeric_limits<size_t>::max())
+{
+    FILE *f = fsbridge::fopen(filename, "rb");
+    if (f == nullptr)
+        return std::make_pair(false,"");
+    std::string retval;
+    char buffer[128];
+    size_t n;
+    while ((n=fread(buffer, 1, sizeof(buffer), f)) > 0) {
+        // Check for reading errors so we don't return any data if we couldn't
+        // read the entire file (or up to maxsize)
+        if (ferror(f)) {
+            fclose(f);
+            return std::make_pair(false,"");
+        }
+        retval.append(buffer, buffer+n);
+        if (retval.size() > maxsize)
+            break;
+    }
+    fclose(f);
+    return std::make_pair(true,retval);
+}
+
+bool WriteBinaryFile(const fs::path &filename, const std::string &data)
+{
+    FILE *f = fsbridge::fopen(filename, "wb");
+    if (f == nullptr)
+        return false;
+    if (fwrite(data.data(), 1, data.size(), f) != data.size()) {
+        fclose(f);
+        return false;
+    }
+    fclose(f);
+    return true;
+}

src/util/readwritefile.h

@@ -0,0 +1,28 @@
+// Copyright (c) 2015-2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_READWRITEFILE_H
+#define BITCOIN_UTIL_READWRITEFILE_H
+
+#include <fs.h>
+
+#include <limits>
+#include <string>
+#include <utility>
+
+/** Read full contents of a file and return them in a std::string.
+ * Returns a pair <status, string>.
+ * If an error occurred, status will be false, otherwise status will be true and the data will be returned in string.
+ *
+ * @param maxsize Puts a maximum size limit on the file that is read. If the file is larger than this, truncated data
+ *         (with len > maxsize) will be returned.
+ */
+std::pair<bool,std::string> ReadBinaryFile(const fs::path &filename, size_t maxsize=std::numeric_limits<size_t>::max());
+
+/** Write contents of std::string to a file.
+ * @return true on success.
+ */
+bool WriteBinaryFile(const fs::path &filename, const std::string &data);
+
+#endif /* BITCOIN_UTIL_READWRITEFILE_H */