Use an array structure to track the temp buffer

1 files changed, 13 insertions, 12 deletions

diff --git a/wikisort.c b/wikisort.c
index 4b01e9b..47e1def 100644
--- a/wikisort.c
+++ b/wikisort.c
@@ -168,22 +168,23 @@ void wikisort(void *unsorted, size_t nmel, size_t width, cmpfun cmp)
 	size_t bcount = nmel / bnmel;
 	size_t bwidth = bnmel * width;
 
-	/* temporary buffer is at base. carve remainder of input into a and b subarrays.
-	 * the nmels for these subarrays is specified in terms of blocks. */
-	size_t bufnmel = bnmel + nmel % bnmel;
-	struct array a = { .base =   base +  width * bufnmel, .nmel = (bcount - 1) / 2 };
-	struct array b = { .base = a.base + bwidth *  a.nmel, .nmel =  bcount - 1 - a.nmel };
+	/* temporary buffer: nmel is measured in array elements */
+	struct array buf = { .base = base, .nmel = bnmel + nmel % bnmel };
+
+	/* A and B subarrays: nmel is measured in blocks of bnmel elements each */
+	struct array a = { .base = buf.base +  width * buf.nmel, .nmel = (bcount - 1) / 2 };
+	struct array b = { .base =   a.base + bwidth *   a.nmel, .nmel =  bcount - 1 - a.nmel };
 
 	/* sort the buffer as if it were part of the a array */
-	wikisort(  base, nmel - b.nmel * bnmel, width, cmp);
-	wikisort(b.base,        b.nmel * bnmel, width, cmp);
+	wikisort(buf.base, buf.nmel + a.nmel * bnmel, width, cmp);
+	wikisort(b.base,              b.nmel * bnmel, width, cmp);
 
 	/* if already sorted, nothing to do */
 	if (cmp(b.base - width, b.base) <= 0) return;
 
 	/* if blocks in b are all less than those in a, just need a rotate */
 	if (cmp(base + (nmel - 1) * width, base) <= 0) {
-		rotate(base, nmel, width, a.nmel * bnmel + bufnmel);
+		rotate(base, nmel, width, a.nmel * bnmel + buf.nmel);
 		return;
 	}
 
@@ -205,7 +206,7 @@ void wikisort(void *unsorted, size_t nmel, size_t width, cmpfun cmp)
 			/* merge any previous pending as and bs */
 			nmel_pend_b -= offset;
 			if (nmel_pend_a && nmel_pend_b) {
-				merge_blocks(base, penda, nmel_pend_a, nmel_pend_b, width, cmp);
+				merge_blocks(buf.base, penda, nmel_pend_a, nmel_pend_b, width, cmp);
 			}
 
 			nmel_pend_a = bnmel;
@@ -224,9 +225,9 @@ void wikisort(void *unsorted, size_t nmel, size_t width, cmpfun cmp)
 	}
 
 	if (nmel_pend_a) {
-		merge_blocks(base, penda, nmel_pend_a, b.nmel * bnmel + nmel_pend_b, width, cmp);
+		merge_blocks(buf.base, penda, nmel_pend_a, b.nmel * bnmel + nmel_pend_b, width, cmp);
 	}
 
-	wikisort(base, bufnmel, width, cmp);
-	distribute_buffer(base, bufnmel, nmel - bufnmel, width, cmp);
+	wikisort(buf.base, buf.nmel, width, cmp);
+	distribute_buffer(buf.base, buf.nmel, nmel - buf.nmel, width, cmp);
 }