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authorMax Horn2010-10-21 09:31:42 +0000
committerMax Horn2010-10-21 09:31:42 +0000
commit66fabfa0492a2f95dd6a0d7f3981ea88007529c1 (patch)
treeed8fe5d9c8828865c4ab7dd2272daa04ec337b31 /engines/scumm/he
parentcca5504b6c7e201c024f0823f0ad151eb8a9b061 (diff)
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SCUMM: Document ScummEngine_v90he::sortArray
svn-id: r53671
Diffstat (limited to 'engines/scumm/he')
-rw-r--r--engines/scumm/he/script_v72he.cpp2
-rw-r--r--engines/scumm/he/script_v90he.cpp27
2 files changed, 23 insertions, 6 deletions
diff --git a/engines/scumm/he/script_v72he.cpp b/engines/scumm/he/script_v72he.cpp
index baa57c7821..bf3146adcd 100644
--- a/engines/scumm/he/script_v72he.cpp
+++ b/engines/scumm/he/script_v72he.cpp
@@ -173,7 +173,7 @@ int ScummEngine_v72he::readArray(int array, int idx2, int idx1) {
}
const int offset = (FROM_LE_32(ah->dim1end) - FROM_LE_32(ah->dim1start) + 1) *
- (idx2 - FROM_LE_32(ah->dim2start)) - FROM_LE_32(ah->dim1start) + idx1;
+ (idx2 - FROM_LE_32(ah->dim2start)) + (idx1 - FROM_LE_32(ah->dim1start));
switch (FROM_LE_32(ah->type)) {
case kByteArray:
diff --git a/engines/scumm/he/script_v90he.cpp b/engines/scumm/he/script_v90he.cpp
index d30804462c..01fbc730e3 100644
--- a/engines/scumm/he/script_v90he.cpp
+++ b/engines/scumm/he/script_v90he.cpp
@@ -1986,6 +1986,13 @@ static int compareDwordArrayReverse(const void *a, const void *b) {
return vb - va;
}
+
+/**
+ * Sort a row range in a two-dimensional array by the value in a given column.
+ *
+ * We sort the data in the row range [dim2start..dim2end], according to the value
+ * in column dim1start == dim1end.
+ */
void ScummEngine_v90he::sortArray(int array, int dim2start, int dim2end, int dim1start, int dim1end, int sortOrder) {
debug(9, "sortArray(%d, [%d,%d,%d,%d], %d)", array, dim2start, dim2end, dim1start, dim1end, sortOrder);
@@ -1994,11 +2001,21 @@ void ScummEngine_v90he::sortArray(int array, int dim2start, int dim2end, int dim
ArrayHeader *ah = (ArrayHeader *)getResourceAddress(rtString, readVar(array));
assert(ah);
- const int num = dim2end - dim2start + 1;
- const int pitch = FROM_LE_32(ah->dim1end) - FROM_LE_32(ah->dim1start) + 1;
- const int offset = pitch * (dim2start - FROM_LE_32(ah->dim2start));
- sortArrayOffset = dim1start - FROM_LE_32(ah->dim1start);
-
+ const int num = dim2end - dim2start + 1; // number of rows to sort
+ const int pitch = FROM_LE_32(ah->dim1end) - FROM_LE_32(ah->dim1start) + 1; // length of a row = number of columns in it
+ const int offset = pitch * (dim2start - FROM_LE_32(ah->dim2start)); // memory offset to the first row to be sorted
+ sortArrayOffset = dim1start - FROM_LE_32(ah->dim1start); // offset to the column by which we sort
+
+ // Now we just have to invoke qsort on the appropriate row range. We
+ // need to pass sortArrayOffset as an implicit parameter to the
+ // comparison functions, which makes it necessary to use a global
+ // (albeit local to this file) variable.
+ // This could be avoided by using qsort_r or a self-written portable
+ // analog (this function passes an additional, user determined
+ // parameter to the comparison function).
+ // Another idea would be to use Common::sort, but that only is
+ // suitable if you sort objects of fixed size, which must be known
+ // during compilation time; clearly this not the case here.
switch (FROM_LE_32(ah->type)) {
case kByteArray:
case kStringArray: