scc

commit 5e82a4f6e2a6beb00682e148ab5d7da555c9aa87
parent a21107f7b0ad490bf153b6c13dc787b997936a7e
Author: Roberto E. Vargas Caballero <k0ga@shike2.com>
Date:   Thu, 23 Nov 2017 22:45:34 +0100

[lib/scc] Add magic number to myro header

It is better to include this field in the header because it makes
the code more orthogonal.

Diffstat:
M
as/myro.c
 | 
7
++-----
M
inc/myro.h
 | 
6
+++++-
M
lib/scc/rmyro.c
 | 
5
++++-
M
lib/scc/wmyro.c
 | 
5
++++-

4 files changed, 15 insertions(+), 8 deletions(-)
diff --git a/as/myro.c b/as/myro.c
@@ -118,14 +118,11 @@ void
 writeout(char *name)
 {
 	FILE *fp;
-	long hdrpos;
-	struct myrohdr hdr = {0};
+	struct myrohdr hdr = { .magic = MYROMAGIC };
 
 	if ((fp = fopen(name, "wb")) == NULL)
 		die("error opening output file '%s'\n", name);
 
-	fputs("uobj", fp);
-	hdrpos = ftell(fp);
 	writehdr(fp, &hdr);
 	hdr.strsize = writestrings(fp);
 	hdr.secsize = writesections(fp);
@@ -133,7 +130,7 @@ writeout(char *name)
 	hdr.relsize = writerelocs(fp);
 	writedata(fp);
 
-	fseek(fp, hdrpos, SEEK_SET);
+	fseek(fp, 0, SEEK_SET);
 	writehdr(fp, &hdr);
 
 	if (fclose(fp))
diff --git a/inc/myro.h b/inc/myro.h
@@ -1,10 +1,14 @@
 
-#define MYROHDR_SIZ    48
+#define MYROHDR_SIZ    52
 #define MYROSECT_SIZ   24
 #define MYROSYM_SIZ    24
 #define MYROREL_SIZ    20
 
+#define MYROMAGIC_SIZ   4
+#define MYROMAGIC      "uobj"
+
 struct myrohdr {
+	char magic[4];
 	unsigned long format;
 	unsigned long long entry;
 	unsigned long long strsize;
diff --git a/lib/scc/rmyro.c b/lib/scc/rmyro.c
@@ -2,6 +2,7 @@ static char sccsid[] = "@(#) ./lib/scc/rmyro.c";
 
 #include <assert.h>
 #include <stdio.h>
+#include <string.h>
 
 #include "../../inc/scc.h"
 #include "../../inc/myro.h"
@@ -15,13 +16,15 @@ readhdr(FILE *fp, struct myrohdr *hdr)
 	fread(buf, sizeof(buf), 1, fp);
 	if (ferror(fp))
 		return EOF;
-	len = lunpack(buf, "lqqqqq",
+	strncpy(hdr->magic, buf, MYROMAGIC_SIZ);
+	len = lunpack(buf + MYROMAGIC_SIZ, "lqqqqq",
 	              &hdr->format,
 	              &hdr->entry,
 	              &hdr->strsize,
 	              &hdr->secsize,
 	              &hdr->symsize,
 	              &hdr->relsize);
+	len += MYROMAGIC_SIZ;
 	assert(len == MYROHDR_SIZ);
 
 	return len;
diff --git a/lib/scc/wmyro.c b/lib/scc/wmyro.c
@@ -2,6 +2,7 @@ static char sccsid[] = "@(#) ./lib/scc/wmyro.c";
 
 #include <assert.h>
 #include <stdio.h>
+#include <string.h>
 
 #include "../../inc/scc.h"
 #include "../../inc/myro.h"
@@ -12,13 +13,15 @@ writehdr(FILE *fp, struct myrohdr *hdr)
 	unsigned char buf[MYROHDR_SIZ];
 	int len;
 
-	len = lpack(buf, "lqqqqq",
+	strncpy(buf, hdr->magic, MYROMAGIC_SIZ);
+	len = lpack(buf + MYROMAGIC_SIZ, "lqqqqq",
 	            hdr->format,
 	            hdr->entry,
 	            hdr->strsize,
 	            hdr->secsize,
 	            hdr->symsize,
 	            hdr->relsize);
+	len += MYROMAGIC_SIZ;
 	assert(MYROHDR_SIZ == len);
 	fwrite(buf, len, 1, fp);