[getInfoHash] Extracted logic to third function

src/DefaultBtProgressInfoFile.cc

@@ -55,9 +55,7 @@
 #include "fmt.h"
 #include "array_fun.h"
 #include "DownloadContext.h"
-#include "BufferedFile.h"
 #include "SHA1IOFile.h"
-#include "BtConstants.h"
 #ifdef ENABLE_BITTORRENT
 #  include "PeerStorage.h"
 #  include "BtRuntime.h"
@@ -223,23 +221,17 @@ void DefaultBtProgressInfoFile::save()
   }
 }
 
-#define READ_CHECK(fp, ptr, count)                                             \
+#define READ_CHECK_STATIC(fp, ptr, count, filename)                            \
   if (fp.read((ptr), (count)) != (count)) {                                    \
-    throw DL_ABORT_EX(fmt(EX_SEGMENT_FILE_READ, filename_.c_str()));           \
+    throw DL_ABORT_EX(fmt(EX_SEGMENT_FILE_READ, filename.c_str()));            \
   }
 
-// It is assumed that integers are saved as:
-// 1) host byte order if version == 0000
-// 2) network byte order if version == 0001
-void DefaultBtProgressInfoFile::load()
+#define READ_CHECK(fp, ptr, count) READ_CHECK_STATIC(fp, ptr, count, filename_)
+
+uint DefaultBtProgressInfoFile::getControlFileVersion(BufferedFile& fp, const std::string& filename)
 {
-  A2_LOG_INFO(fmt(MSG_LOADING_SEGMENT_FILE, filename_.c_str()));
-  BufferedFile fp(filename_.c_str(), BufferedFile::READ);
-  if (!fp) {
-    throw DL_ABORT_EX(fmt(EX_SEGMENT_FILE_READ, filename_.c_str()));
-  }
   unsigned char versionBuf[2];
-  READ_CHECK(fp, versionBuf, sizeof(versionBuf));
+  READ_CHECK_STATIC(fp, versionBuf, sizeof(versionBuf), filename);
   std::string versionHex = util::toHex(versionBuf, sizeof(versionBuf));
   int version;
   if ("0000" == versionHex) {
@@ -252,6 +244,53 @@ void DefaultBtProgressInfoFile::load()
     throw DL_ABORT_EX(
         fmt("Unsupported ctrl file version: %s", versionHex.c_str()));
   }
+
+  return version;
+}
+
+std::array<unsigned char, INFO_HASH_LENGTH> DefaultBtProgressInfoFile::getInfoHash(const std::string& control_file)
+{
+  A2_LOG_INFO(fmt(MSG_LOADING_SEGMENT_FILE, control_file.c_str()));
+  BufferedFile fp(control_file.c_str(), BufferedFile::READ);
+  if (!fp) {
+    throw DL_ABORT_EX(fmt(EX_SEGMENT_FILE_READ, control_file.c_str()));
+  }
+  
+  auto version = getControlFileVersion(fp, control_file);
+
+  unsigned char extension[4];
+  READ_CHECK_STATIC(fp, extension, sizeof(extension), control_file);
+
+  uint32_t infoHashLength;
+  READ_CHECK_STATIC(fp, &infoHashLength, sizeof(infoHashLength), control_file);
+  if (version >= 1) {
+    infoHashLength = ntohl(infoHashLength);
+  }
+  if (infoHashLength != INFO_HASH_LENGTH) {
+    throw DL_ABORT_EX(fmt("Invalid info hash length: %d", infoHashLength));
+  }
+
+  std::array<unsigned char, INFO_HASH_LENGTH> savedInfoHash;
+  if (infoHashLength > 0) {
+    READ_CHECK_STATIC(fp, savedInfoHash.data(), infoHashLength, control_file);
+  }
+
+  return savedInfoHash;
+}
+
+// It is assumed that integers are saved as:
+// 1) host byte order if version == 0000
+// 2) network byte order if version == 0001
+void DefaultBtProgressInfoFile::load()
+{
+  A2_LOG_INFO(fmt(MSG_LOADING_SEGMENT_FILE, filename_.c_str()));
+  BufferedFile fp(filename_.c_str(), BufferedFile::READ);
+  if (!fp) {
+    throw DL_ABORT_EX(fmt(EX_SEGMENT_FILE_READ, filename_.c_str()));
+  }
+
+  auto version = getControlFileVersion(fp, filename_);
+
   unsigned char extension[4];
   READ_CHECK(fp, extension, sizeof(extension));
   bool infoHashCheckEnabled = false;

src/DefaultBtProgressInfoFile.h

@@ -36,6 +36,8 @@
 #define D_DEFAULT_BT_PROGRESS_INFO_FILE_H
 
 #include "BtProgressInfoFile.h"
+#include "BufferedFile.h"
+#include "BtConstants.h"
 
 #include <memory>
 
@@ -93,6 +95,11 @@ public:
   void setBtRuntime(const std::shared_ptr<BtRuntime>& btRuntime);
 #endif // ENABLE_BITTORRENT
 
+  // Assume getting pointer to the start of the file
+  static uint getControlFileVersion(BufferedFile& fp, const std::string& filename);
+
+  static std::array<unsigned char, INFO_HASH_LENGTH> getInfoHash(const std::string& control_file);
+
   static const std::string& getSuffix()
   {
     static std::string suffix = ".aria2";