From ec74cb650ce50947f7eb792bf6c165a7b30236b7 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Sat, 19 Mar 2016 12:01:01 -0400
Subject: [PATCH] Attempt to write an iterator for the multiboot memory map
 list

---
 src/Multiboot.cc | 95 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/Multiboot.hh | 51 ++++++++++++++++++++------
 2 files changed, 134 insertions(+), 12 deletions(-)

diff --git a/src/Multiboot.cc b/src/Multiboot.cc
index f8cc266..cda50be 100644
--- a/src/Multiboot.cc
+++ b/src/Multiboot.cc
@@ -52,6 +52,71 @@ Information::setInformation(Information *info)
  * Public
  */
 
+Information::MemoryMapIterator::MemoryMapIterator(uint32_t address,
+                                                  uint32_t count)
+    : mCurrent(reinterpret_cast<MemoryChunk *>(address)),
+      mCount(count)
+{ }
+
+
+Information::MemoryMapIterator::MemoryMapIterator(const MemoryMapIterator& other)
+    : mCurrent(other.mCurrent),
+      mCount(other.mCount)
+{ }
+
+
+Information::MemoryMapIterator&
+Information::MemoryMapIterator::operator++()
+{
+    if (mCount > 0) {
+        auto p = reinterpret_cast<uint32_t *>(mCurrent);
+        // The size of the current struct is stored at (mCurrent - 4) bytes.
+        mCurrent = (mCurrent + p[-1]);
+        mCount--;
+    }
+    return *this; 
+}
+
+
+Information::MemoryMapIterator
+Information::MemoryMapIterator::operator++(int)
+{
+    MemoryMapIterator tmp(reinterpret_cast<uint32_t>(mCurrent), mCount);
+    operator++();
+    return tmp;
+}
+
+
+MemoryChunk
+Information::MemoryMapIterator::operator*()
+{
+    if (mCount == 0) {
+        return MemoryChunk{0, 0, 0};
+    }
+    return *mCurrent;
+}
+
+
+bool
+Information::MemoryMapIterator::operator==(const MemoryMapIterator& other)
+    const
+{
+    if (mCount == 0 && other.mCount == 0) {
+        // If both iterators have 0 counts, it doesn't matter what the mCurrent members point at.
+        return true;
+    }
+    return mCurrent == other.mCurrent && mCount == other.mCount;
+}
+
+
+bool
+Information::MemoryMapIterator::operator!=(const MemoryMapIterator& other)
+    const
+{
+    return !(*this == other);
+}
+
+
 uint32_t
 Information::lowerMemoryKB()
     const
@@ -83,5 +148,35 @@ Information::commandLine()
     }
     return reinterpret_cast<const char *>(mCommandLine);
 }
+
+
+uint32_t
+Information::memoryMapChunks()
+    const
+{
+    if ((mFlags & Present::MemoryMap) == 0) {
+        return 0;
+    }
+    return memoryMapCount;
+}
+
+
+Information::MemoryMapIterator
+Information::memoryMapBegin()
+    const
+{
+    if ((mFlags & Present::MemoryMap) == 0) {
+        return memoryMapEnd();
+    }
+    return MemoryMapIterator(memoryMapAddress, memoryMapCount);
+}
+
+
+Information::MemoryMapIterator
+Information::memoryMapEnd()
+    const
+{
+    return {0, 0};
+}
     
 } /* namespace multiboot */
diff --git a/src/Multiboot.hh b/src/Multiboot.hh
index 72b42d5..a9185cc 100644
--- a/src/Multiboot.hh
+++ b/src/Multiboot.hh
@@ -15,19 +15,51 @@
 
 namespace multiboot {
 
+struct PACKED MemoryChunk
+{
+    /** Base address of the chunk of memory. */
+    uint64_t base;
+    /** Length of the chunk of memory, in bytes. */
+    uint64_t length;
+    /** Type of address range. 1 indicates available; all other values indicate reserved memory. */
+    uint32_t type;
+};
+
 /**
  * The multiboot information struct. Defined by the multiboot spec.
  * See http://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Machine-state
  */
 struct PACKED Information
 {
+    struct MemoryMapIterator
+    {
+        MemoryMapIterator(uint32_t address, uint32_t count);
+        MemoryMapIterator(const MemoryMapIterator& other);
+
+        MemoryMapIterator& operator++();
+        MemoryMapIterator operator++(int);
+        MemoryChunk operator*();
+
+        bool operator==(const MemoryMapIterator& other) const;
+        bool operator!=(const MemoryMapIterator& other) const;
+
+    private:
+        MemoryChunk *mCurrent;
+        uint32_t mCount;
+    };
+
     static const Information *information();
     static void setInformation(Information* info);
 
     uint32_t lowerMemoryKB() const;
     uint32_t upperMemoryKB() const;
+
     const char* commandLine() const;
 
+    uint32_t memoryMapChunks() const;
+    MemoryMapIterator memoryMapBegin() const;
+    MemoryMapIterator memoryMapEnd() const;
+
 private:
     /**
      * Bit field of flags. Fields below are only defined if the appropriate
@@ -98,16 +130,16 @@ private:
     } symbols;
 
     /**
+     * @defgroup Memory Map
      * Points to a buffer containing a memory map of the machine provided by the
      * BIOS. Defined only if `memoryMapPresent == true`.
+     * @{
      */
-    struct PACKED
-    {
-        /** Number of memory map entries present. */
-        uint32_t count;
-        /** Pointer to start of memory map entry array. */
-        uint32_t address;
-    } memoryMap;
+    /** Number of memory map entries present. */
+    uint32_t memoryMapCount;
+    /** Pointer to start of memory map entry array. */
+    uint32_t memoryMapAddress;
+    /** @} */
 
     /**
      * Points to a buffer containing a list of drive definitions provided by the
@@ -152,11 +184,6 @@ struct PACKED Module
     uint32_t reserved;
 };
 
-// TODO: Define the MemoryMap struct
-struct PACKED MemoryChunk
-{
-};
-
 // TODO: Define the Drive struct
 struct PACKED Drive
 {