+/*
+ * Test to see if any blocks in a range are allocated.
+ *
+ * The journal or allocation file lock must be held.
+ */
+__private_extern__
+int
+hfs_isallocated(struct hfsmount *hfsmp, u_long startingBlock, u_long numBlocks)
+{
+ u_int32_t *currentWord; // Pointer to current word within bitmap block
+ u_int32_t wordsLeft; // Number of words left in this bitmap block
+ u_int32_t bitMask; // Word with given bits already set (ready to test)
+ u_int32_t firstBit; // Bit index within word of first bit to allocate
+ u_int32_t numBits; // Number of bits in word to allocate
+ u_int32_t *buffer = NULL;
+ u_int32_t blockRef;
+ u_int32_t bitsPerBlock;
+ u_int32_t wordsPerBlock;
+ int inuse = 0;
+ int error;
+
+ /*
+ * Pre-read the bitmap block containing the first word of allocation
+ */
+ error = ReadBitmapBlock(hfsmp, startingBlock, &buffer, &blockRef);
+ if (error)
+ return (error);
+
+ /*
+ * Initialize currentWord, and wordsLeft.
+ */
+ {
+ u_int32_t wordIndexInBlock;
+
+ bitsPerBlock = hfsmp->vcbVBMIOSize * kBitsPerByte;
+ wordsPerBlock = hfsmp->vcbVBMIOSize / kBytesPerWord;
+
+ wordIndexInBlock = (startingBlock & (bitsPerBlock-1)) / kBitsPerWord;
+ currentWord = buffer + wordIndexInBlock;
+ wordsLeft = wordsPerBlock - wordIndexInBlock;
+ }
+
+ /*
+ * First test any non word aligned bits.
+ */
+ firstBit = startingBlock % kBitsPerWord;
+ if (firstBit != 0) {
+ bitMask = kAllBitsSetInWord >> firstBit;
+ numBits = kBitsPerWord - firstBit;
+ if (numBits > numBlocks) {
+ numBits = numBlocks;
+ bitMask &= ~(kAllBitsSetInWord >> (firstBit + numBits));
+ }
+ if ((*currentWord & SWAP_BE32 (bitMask)) != 0) {
+ inuse = 1;
+ goto Exit;
+ }
+ numBlocks -= numBits;
+ ++currentWord;
+ --wordsLeft;
+ }
+
+ /*
+ * Test whole words (32 blocks) at a time.
+ */
+ while (numBlocks >= kBitsPerWord) {
+ if (wordsLeft == 0) {
+ /* Read in the next bitmap block. */
+ startingBlock += bitsPerBlock;
+
+ buffer = NULL;
+ error = ReleaseBitmapBlock(hfsmp, blockRef, false);
+ if (error) goto Exit;
+
+ error = ReadBitmapBlock(hfsmp, startingBlock, &buffer, &blockRef);
+ if (error) goto Exit;
+
+ /* Readjust currentWord and wordsLeft. */
+ currentWord = buffer;
+ wordsLeft = wordsPerBlock;
+ }
+ if (*currentWord != 0) {
+ inuse = 1;
+ goto Exit;
+ }
+ numBlocks -= kBitsPerWord;
+ ++currentWord;
+ --wordsLeft;
+ }
+
+ /*
+ * Test any remaining blocks.
+ */
+ if (numBlocks != 0) {
+ bitMask = ~(kAllBitsSetInWord >> numBlocks);
+ if (wordsLeft == 0) {
+ /* Read in the next bitmap block */
+ startingBlock += bitsPerBlock;
+
+ buffer = NULL;
+ error = ReleaseBitmapBlock(hfsmp, blockRef, false);
+ if (error) goto Exit;
+
+ error = ReadBitmapBlock(hfsmp, startingBlock, &buffer, &blockRef);
+ if (error) goto Exit;
+
+ currentWord = buffer;
+ wordsLeft = wordsPerBlock;
+ }
+ if ((*currentWord & SWAP_BE32 (bitMask)) != 0) {
+ inuse = 1;
+ goto Exit;
+ }
+ }
+Exit:
+ if (buffer) {
+ (void)ReleaseBitmapBlock(hfsmp, blockRef, false);
+ }
+ return (inuse);
+}
+
projects / apple / xnu.git / blobdiff