Rewrite calculateChecksum(), add tests

Author: Optiroc

.vscode/launch.json

@@ -1,13 +1,15 @@
 {
-    "version": "0.2.0",
-    "configurations": [
-        {
-            "name": "Debug",
-            "type": "lldb",
-            "request": "launch",
-            "program": "${workspaceFolder}/build/superfamicheck",
-            "args": ["test/data/public/rom1.sfc"],
-            "preLaunchTask": "${defaultBuildTask}"
-        }
-    ]
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "Debug",
+      "type": "lldb",
+      "request": "launch",
+      "program": "${workspaceFolder}/build/superfamicheck",
+      "args": [
+        "test/data/public/rom1.sfc"
+      ],
+      "preLaunchTask": "${defaultBuildTask}",
+    }
+  ]
 }

README.md

@@ -5,7 +5,7 @@ superfamicheck is programmed by David Lindecrantz and distributed under the term
 
 
 ## building
-in a unix-like environment simply `make` the binary. on windows use cmake to generate a build environment.
+use cmake to generate a build environment, or simply type `make` which will run cmake for you.
 
 ## operation
 

src/sfcRom.cpp

@@ -92,14 +92,16 @@ sfcRom::sfcRom(const string& path) {
   {
     if ((mode & 0xe0) != 0x20) {
       correctedMode = headerLocation >= 0x8000 ? 0x21 : 0x20;
-      hasLegalMode = false;
       hasSevereIssues = true;
       ++issues;
+    } else {
+      hasLegalMode = true;
     }
 
     if (mapperName.empty()) {
-      hasKnownMapper = false;
       ++issues;
+    } else {
+      hasKnownMapper = true;
     }
   }
 
@@ -124,17 +126,20 @@ sfcRom::sfcRom(const string& path) {
   // Check RAM size
   {
     if ((hasRam && ramSize > 0x0f) || (!hasRam && ramSize != 0)) {
-      hasCorrectRamSize = false;
       ++issues;
+    } else {
+      hasCorrectRamSize = true;
     }
   }
 
   // Calculate checksum
   {
     correctedChecksum = calculateChecksum();
     correctedComplement = ~correctedChecksum;
-    if (checksum != correctedChecksum) {
+    if ((checksum != correctedChecksum) || complement != correctedComplement) {
       ++issues;
+    } else {
+      hasCorrectChecksum = true;
     }
   }
 
@@ -246,7 +251,7 @@ string sfcRom::description(bool silent) const {
           os << "  RAM size should be 0x00" << '\n';
         }
       }
-      if (checksum != correctedChecksum || complement != correctedComplement) {
+      if (!hasCorrectChecksum) {
         os << "  Checksum/complement should be 0x" << setw(4) << correctedChecksum << "/0x" << setw(4) << correctedComplement
            << '\n';
       }
@@ -621,58 +626,53 @@ void sfcRom::getHeaderInfo(const vector<uint8_t>& header) {
 }
 
 uint16_t sfcRom::calculateChecksum() const {
-  size_t imageSize = image.size();
-  size_t mappedSize;
+  vector<uint8_t> img = image;
+  putWord(img, headerLocation + 0x2c, 0xffff);
+  putWord(img, headerLocation + 0x2e, 0x0000);
 
-  // Base and mask for out of bounds mirroring
-  uint32_t base = 0;
-  uint32_t offsetMask = 0xffffffff;
-  uint32_t offsetMod = 0xffffffff;
+  size_t imageSize = img.size();
+  size_t mappedSize;
 
   if (mapper == 0x0a && chipset == 0xf9 && chipsetSubtype == 0x00) {
     // Extended HiROM/SPC7110+RTC+Battery
     mappedSize = imageSize;
   } else if (mapper == 0x0a && chipset == 0xf5 && chipsetSubtype == 0x00) {
     // Extended HiROM/SPC7110+Battery
     mappedSize = imageSize > 0x200000 ? imageSize << 1 : imageSize;
-    offsetMod = imageSize;
+    while (mappedSize > img.size()) {
+      size_t remaining = mappedSize - img.size();
+      if (remaining > image.size()) {
+        remaining = image.size();
+      }
+      if ((remaining + img.size()) > mappedSize) {
+        remaining = mappedSize - img.size();
+      }
+      vector<uint8_t> mirror(img.begin(), img.begin() + remaining);
+      img.insert(img.end(), mirror.begin(), mirror.end());
+    }
   } else {
+    // Standard mapping
     mappedSize = 1 << (correctedRomSize != 0 ? correctedRomSize + 10 : romSize + 10);
-    uint32_t mask = 1;
-    uint32_t t = imageSize;
-    while (t >>= 1) {
-      mask <<= 1;
-      mask += 1;
+    while (mappedSize > img.size()) {
+      vector<uint8_t> mirror(img.begin() + (mappedSize >> 1), img.end());
+      img.insert(img.end(), mirror.begin(), mirror.end());
     }
-    mask >>= 1;
-    base = mask + 1;
-    offsetMask = imageSize - base - 1;
   }
 
-  // Add sum
-  auto img = image;
-  putWord(img, headerLocation + 0x2c, 0xffff);
-  putWord(img, headerLocation + 0x2e, 0x0000);
   uint16_t sum = 0;
-
-  for (size_t offset = 0; offset < mappedSize; ++offset) {
-    size_t imgOffset = offset % offsetMod;
-    if (imgOffset < imageSize) {
-      sum += img[imgOffset];
-    } else {
-      size_t mirrorOffset = base + (imgOffset & offsetMask);
-      sum += img[mirrorOffset];
-    }
+  size_t length = img.size();
+  for (size_t offset = 0; offset < length; ++offset) {
+    sum += img[offset];
   }
   return sum;
 }
 
-
-// Get/put little endian word
+// Get little endian word
 uint16_t getWord(const vector<uint8_t>& vec, size_t offset) {
   return (uint16_t)((vec[offset]) + ((uint8_t)(vec[offset + 1]) << 8));
 }
 
+// Put little endian word
 void putWord(vector<uint8_t>& vec, size_t offset, uint16_t value) {
   vec[offset] = (uint8_t)(value & 0xff);
   vec[offset + 1] = (uint8_t)(value >> 8);

src/sfcRom.hpp

@@ -16,9 +16,10 @@ struct sfcRom {
 
   bool hasCopierHeader = false;
   bool hasCorrectTitle = false;
-  bool hasCorrectRamSize = true;
-  bool hasLegalMode = true;
-  bool hasKnownMapper = true;
+  bool hasCorrectRamSize = false;
+  bool hasCorrectChecksum = false;
+  bool hasLegalMode = false;
+  bool hasKnownMapper = false;
   bool hasNewFormatHeader = false;
 
   std::string title;
@@ -29,19 +30,28 @@ struct sfcRom {
   std::string version;
   std::string country;
 
-  uint8_t mode;
-  uint8_t mapper;
-  bool fast;
+  uint8_t mode = 0;
+  uint8_t mapper = 0;
+  bool fast = false;
   bool hasRam = false;
 
-  uint8_t chipset;
+  uint8_t chipset = 0;
   uint8_t chipsetSubtype = 0;
-  uint8_t romSize;
-  uint8_t ramSize;
-  uint8_t countryCode;
+  uint8_t romSize = 0;
+  uint8_t ramSize = 0;
+  uint8_t countryCode = 0;
 
-  uint16_t checksum;
-  uint16_t complement;
+  uint16_t checksum = 0;
+  uint16_t complement = 0;
+
+  size_t imageSize = 0;
+  size_t imageOffset = 0;
+  size_t headerLocation = 0;
+
+  uint8_t correctedMode = 0;
+  uint8_t correctedRomSize = 0;
+  uint16_t correctedChecksum = 0;
+  uint16_t correctedComplement = 0;
 
 private:
   std::string filepath;
@@ -50,13 +60,4 @@ struct sfcRom {
   void getHeaderInfo(const std::vector<uint8_t>& header);
   int scoreHeaderLocation(size_t location) const;
   uint16_t calculateChecksum() const;
-
-  size_t imageSize;
-  size_t imageOffset = 0;
-  size_t headerLocation = 0;
-
-  uint8_t correctedMode = 0;
-  uint8_t correctedRomSize = 0;
-  uint16_t correctedChecksum;
-  uint16_t correctedComplement;
 };