Allow capping the number of threads

common.c

@@ -333,6 +333,8 @@ queue_t *gPipelineStartQ = NULL,
     *gPipelineSplitQ = NULL,
     *gPipelineMergeQ = NULL;
 
+size_t gPipelineProcessMax = 0;
+
 pipeline_data_free_t gPLFreer = NULL;
 pipeline_split_t gPLSplit = NULL;
 pipeline_process_t gPLProcess = NULL;
@@ -367,6 +369,9 @@ void pipeline_create(
     gPLMergedItems = NULL;
     
     gPLProcessCount = num_threads();
+	if (gPipelineProcessMax > 0 && gPipelineProcessMax < gPLProcessCount)
+		gPLProcessCount = gPipelineProcessMax;
+	
     gPLProcessThreads = malloc(gPLProcessCount * sizeof(pthread_t));
     for (size_t i = 0; i < (int)(gPLProcessCount * 2 + 3); ++i) {
         // create blocks, including a margin of error

pixz.c

@@ -55,7 +55,9 @@ int main(int argc, char **argv) {
     char *ipath = NULL, *opath = NULL;
     
     int ch;
-    while ((ch = getopt(argc, argv, "dxli:o:tvh0123456789")) != -1) {
+	char *optend;
+	long optint;
+    while ((ch = getopt(argc, argv, "dxli:o:tvhp:0123456789")) != -1) {
         switch (ch) {
             case 'd': op = OP_READ; break;
             case 'x': op = OP_EXTRACT; break;
@@ -63,7 +65,13 @@ int main(int argc, char **argv) {
             case 'i': ipath = optarg; break;
             case 'o': opath = optarg; break;
             case 't': tar = false; break;
-			case 'h': usage(NULL);
+			case 'h': usage(NULL); break;
+			case 'p':
+				optint = strtol(optarg, &optend, 10);
+				if (optint < 0 || *optend)
+					usage("Need a non-negative integer argument to -p");
+				gPipelineProcessMax = optint;
+				break;
             default:
                 if (ch >= '0' && ch <= '9') {
                     level = ch - '0';

pixz.h

@@ -106,6 +106,7 @@ int queue_pop(queue_t *q, void **datap);
 
 #pragma mark PIPELINE
 
+extern size_t gPipelineProcessMax;
 extern queue_t *gPipelineStartQ, *gPipelineSplitQ, *gPipelineMergeQ;
 
 typedef enum {