Start working on parallel read

Makefile

@@ -16,7 +16,7 @@ CC = gcc
 COMPILE = $(CC) $(CFLAGS) -c -o
 LD = $(CC) $(LDFLAGS) -o
 
-PROGS = write read list
+PROGS = write read list pread
 COMMON = common.o endian.o cpu.o
 
 all: $(PROGS)

common.c

@@ -40,6 +40,7 @@ void *decode_block_start(off_t block_seek) {
     if (fseeko(gInFile, block_seek, SEEK_SET) == -1)
         die("Error seeking to block");
     
+    // Some memory in which to keep the discovered filters safe
     block_wrapper_t *bw = malloc(sizeof(block_wrapper_t));
     bw->block = (lzma_block){ .check = gCheck, .filters = bw->filters,
 	 	.version = 0 };
@@ -94,7 +95,7 @@ void free_file_index(void) {
     gFileIndex = gLastFile = NULL;
 }
 
-bool read_file_index(void) {
+lzma_vli find_file_index(void **bdatap) {
     if (!gIndex)
         decode_index();
         
@@ -112,10 +113,29 @@ bool read_file_index(void) {
     
     // Check if this is really an index
     read_file_index_data();
-    if (xle64dec(gFileIndexBuf + gFIBPos) != PIXZ_INDEX_MAGIC) {
+    lzma_vli ret = iter.block.compressed_file_offset;
+    if (xle64dec(gFileIndexBuf + gFIBPos) != PIXZ_INDEX_MAGIC)
+        ret = 0;
+    
+    if (bdatap && ret) {
+        *bdatap = bdata;
+    } else {
+        // Just looking, don't keep things around
+        if (bdatap)
+            *bdatap = NULL;
+        free(bdata);
+        free(gFileIndexBuf);
         gLastFile = gFileIndex = NULL;
-        return false;
+        lzma_end(&gStream);
     }
+    return ret; 
+}  
+
+bool read_file_index(void) {
+    void *bdata;
+    find_file_index(&bdata);
+    if (!bdata)
+        return false;
     
     while (true) {
         char *name = read_file_index_name();

pixz.h

@@ -52,6 +52,7 @@ extern file_index_t *gFileIndex, *gLastFile;
 
 void decode_index(void);
 
+lzma_vli find_file_index(void **bdatap);
 bool read_file_index(void);
 void dump_file_index(FILE *out);
 void free_file_index(void);

pread.c

@@ -0,0 +1,40 @@
+#include "pixz.h"
+
+/* TODO
+ * - parallel extraction
+ * - restrict to certain files
+ * - verify file-index matches archive contents
+ */
+
+static FILE *gOutFile = NULL;
+
+static size_t largest_block_size();
+
+int main(int argc, char **argv) {
+    // TODO: Arguments?
+    gInFile = stdin;
+    gOutFile = stdout;
+    
+    // Find largest block size
+    size_t blocksize = largest_block_size();
+    printf("block size: %zu\n", blocksize);
+    
+    return 0;
+}
+
+static size_t largest_block_size() {
+    // exclude the index block
+    lzma_vli index_offset = find_file_index(NULL);
+    
+    lzma_index_iter iter;
+    lzma_index_iter_init(&iter, gIndex);
+    
+    size_t largest = 0;
+    while (!lzma_index_iter_next(&iter, LZMA_INDEX_ITER_BLOCK)) {
+        if (index_offset && iter.block.compressed_file_offset == index_offset)
+            continue;
+        if (iter.block.uncompressed_size > largest)
+            largest = iter.block.uncompressed_size;
+    }
+    return largest;
+}