tools: add "blkdown" tool

When developing from a Collapse OS environment, it's necessary to
be able to download blocks from it.

tools/Makefile

@@ -6,9 +6,10 @@ EXEC_TGT = exec
 BLKPACK_TGT = blkpack
 BLKUNPACK_TGT = blkunpack
 BLKUP_TGT = blkup
+BLKDOWN_TGT = blkdown
 TARGETS = $(MEMDUMP_TGT) $(UPLOAD_TGT) \
 	$(TTYSAFE_TGT) $(PINGPONG_TGT) $(EXEC_TGT) $(BLKPACK_TGT) \
-    $(BLKUNPACK_TGT) $(BLKUP_TGT)
+    $(BLKUNPACK_TGT) $(BLKUP_TGT) $(BLKDOWN_TGT)
 OBJS = common.o
 
 all: $(TARGETS)
@@ -25,6 +26,7 @@ $(EXEC_TGT): $(EXEC_TGT).c
 $(BLKPACK_TGT): $(BLKPACK_TGT).c
 $(BLKUNPACK_TGT): $(BLKUNPACK_TGT).c
 $(BLKUP_TGT): $(BLKUP_TGT).c
+$(BLKDOWN_TGT): $(BLKDOWN_TGT).c
 $(TARGETS): $(OBJS)
 	$(CC) $(CFLAGS) $@.c $(OBJS) -o $@
 

tools/blkdown.c

@@ -0,0 +1,60 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+
+#include "common.h"
+
+/* Pull specified block no "srcblk" from "device" into block no "dstblk" in
+ * local "blkfs". If "dstblk" is omitted, it is the same as "srcblk"
+ */
+
+int main(int argc, char **argv)
+{
+    if ((argc != 5) && (argc != 4)) {
+        fprintf(stderr, "Usage: ./blkdown device srcblk blkfs [dstblk]\n");
+        return 1;
+    }
+    unsigned int srcblk = strtol(argv[2], NULL, 10);
+    unsigned int dstblk = srcblk;
+    if (argc == 5) {
+        dstblk = strtol(argv[4], NULL, 10);
+    }
+    FILE *fp = fopen(argv[3], "r+");
+    if (!fp) {
+        fprintf(stderr, "Can't open %s.\n", argv[3]);
+        return 1;
+    }
+    int fd = ttyopen(argv[1]);
+    if (fd < 0) {
+        fprintf(stderr, "Could not open %s\n", argv[1]);
+        return 1;
+    }
+    fseek(fp, 1024 * dstblk, SEEK_SET);
+    char s[0x40];
+    sprintf(s, ": _ %d BLK@ 1024 0 DO I BLK( + C@ .x LOOP ; _", srcblk);
+    sendcmd(fd, s);
+
+    int returncode = 0;
+    for (int i=0; i<1024; i++) {
+        usleep(1000); // let it breathe
+        mread(fd, s, 2); // read hex pair
+        s[2] = 0; // null terminate
+        char *endptr = NULL;
+        unsigned char c = strtol(s, &endptr, 16);
+        if (endptr != &s[2]) {
+            fprintf(stderr, "Non-hex value (%s) at index %d.\n", s, i);
+            // we don't exit now because we need to "consume" our whole program.
+            returncode = 1;
+        }
+        if (returncode == 0) {
+            fwrite(&c, 1, 1, fp);
+        }
+    }
+    readprompt(fd);
+    sendcmdp(fd, "FORGET _");
+    printf("Done!\n");
+    fclose(fp);
+    return returncode;
+}