dev: Use the correct return type for disk offsets

Replace the use of off_t in the various DiskImage related classes with
std::streampos. off_t is a signed 32 bit integer on most 32-bit
systems, whereas std::streampos is normally a 64 bit integer on most
modern systems. Furthermore, std::streampos is the type used by
tellg() and seekg() in the standard library, so it should have been
used in the first place. This patch makes it possible to use disk
images larger than 2 GiB on 32 bit systems with a modern C++ standard
library.

src/dev/disk_image.cc

@@ -86,7 +86,7 @@ RawDiskImage::close()
     stream.close();
 }
 
-off_t
+std::streampos
 RawDiskImage::size() const
 {
     if (disk_size == 0) {
@@ -99,8 +99,8 @@ RawDiskImage::size() const
     return disk_size / SectorSize;
 }
 
-off_t
-RawDiskImage::read(uint8_t *data, off_t offset) const
+std::streampos
+RawDiskImage::read(uint8_t *data, std::streampos offset) const
 {
     if (!initialized)
         panic("RawDiskImage not initialized");
@@ -120,8 +120,8 @@ RawDiskImage::read(uint8_t *data, off_t offset) const
     return stream.tellg() - pos;
 }
 
-off_t
-RawDiskImage::write(const uint8_t *data, off_t offset)
+std::streampos
+RawDiskImage::write(const uint8_t *data, std::streampos offset)
 {
     if (!initialized)
         panic("RawDiskImage not initialized");
@@ -357,12 +357,12 @@ CowDiskImage::writeback()
     }
 }
 
-off_t
+std::streampos
 CowDiskImage::size() const
 { return child->size(); }
 
-off_t
-CowDiskImage::read(uint8_t *data, off_t offset) const
+std::streampos
+CowDiskImage::read(uint8_t *data, std::streampos offset) const
 {
     if (!initialized)
         panic("CowDiskImage not initialized");
@@ -381,8 +381,8 @@ CowDiskImage::read(uint8_t *data, off_t offset) const
     }
 }
 
-off_t
-CowDiskImage::write(const uint8_t *data, off_t offset)
+std::streampos
+CowDiskImage::write(const uint8_t *data, std::streampos offset)
 {
     if (!initialized)
         panic("RawDiskImage not initialized");

src/dev/disk_image.hh

@@ -58,10 +58,12 @@ class DiskImage : public SimObject
     DiskImage(const Params *p) : SimObject(p), initialized(false) {}
     virtual ~DiskImage() {}
 
-    virtual off_t size() const = 0;
+    virtual std::streampos size() const = 0;
 
-    virtual off_t read(uint8_t *data, off_t offset) const = 0;
-    virtual off_t write(const uint8_t *data, off_t offset) = 0;
+    virtual std::streampos read(uint8_t *data,
+                                std::streampos offset) const = 0;
+    virtual std::streampos write(const uint8_t *data,
+                                 std::streampos offset) = 0;
 };
 
 /**
@@ -73,7 +75,7 @@ class RawDiskImage : public DiskImage
     mutable std::fstream stream;
     std::string file;
     bool readonly;
-    mutable off_t disk_size;
+    mutable std::streampos disk_size;
 
   public:
     typedef RawDiskImageParams Params;
@@ -83,10 +85,10 @@ class RawDiskImage : public DiskImage
     void close();
     void open(const std::string &filename, bool rd_only = false);
 
-    virtual off_t size() const;
+    virtual std::streampos size() const;
 
-    virtual off_t read(uint8_t *data, off_t offset) const;
-    virtual off_t write(const uint8_t *data, off_t offset);
+    virtual std::streampos read(uint8_t *data, std::streampos offset) const;
+    virtual std::streampos write(const uint8_t *data, std::streampos offset);
 };
 
 /**
@@ -129,10 +131,10 @@ class CowDiskImage : public DiskImage
     void serialize(std::ostream &os);
     void unserialize(Checkpoint *cp, const std::string &section);
 
-    virtual off_t size() const;
+    virtual std::streampos size() const;
 
-    virtual off_t read(uint8_t *data, off_t offset) const;
-    virtual off_t write(const uint8_t *data, off_t offset);
+    virtual std::streampos read(uint8_t *data, std::streampos offset) const;
+    virtual std::streampos write(const uint8_t *data, std::streampos offset);
 };
 
 #endif // __DISK_IMAGE_HH__

src/dev/ide_disk.cc

@@ -590,7 +590,7 @@ IdeDisk::startCommand()
     switch (cmdReg.command) {
         // Supported non-data commands
       case WDSF_READ_NATIVE_MAX:
-        size = image->size() - 1;
+        size = (uint32_t)image->size() - 1;
         cmdReg.sec_num = (size & 0xff);
         cmdReg.cyl_low = ((size & 0xff00) >> 8);
         cmdReg.cyl_high = ((size & 0xff0000) >> 16);