From 358691759871264951bcacb3066340030466d93d Mon Sep 17 00:00:00 2001
From: Nick Bowler <nbowler@draconx.ca>
Date: Fri, 5 Jun 2009 15:18:49 -0400
Subject: [PATCH] Implement export table parsing.

---
 libupkg.c | 127 +++++++++++++++++++++++++++++++++++++++++++++++++-----
 upkg.c    |   2 +
 2 files changed, 118 insertions(+), 11 deletions(-)

diff --git a/libupkg.c b/libupkg.c
index de4b2f1..f55c079 100644
--- a/libupkg.c
+++ b/libupkg.c
@@ -5,31 +5,63 @@
 #include "upkg.h"
 #include "pack.h"
 
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
 struct upkg_name {
 	unsigned long flags;
 	char *name;
 };
 
+struct upkg_export {
+	long class, super, name;
+	unsigned long package, flags;
+	unsigned long size, offset;
+};
+
 struct upkg_private {
 	FILE *f;
 
-	struct upkg_name *names;
+	struct upkg_name   *names;
+	struct upkg_export *exports;
 
 	unsigned long name_offset, export_offset, import_offset;
 	unsigned char guid[16];
 };
 
-static long decode_index(unsigned char *bytes)
+/*
+ * Decode the compact index format from the upkg.  This format is fucked.
+ * Stores the result in *val and returns the number of input bytes read (or 0
+ * if the input is invalid, in which case *val is undefined).
+ */
+static size_t decode_index(long *val, unsigned char *bytes, size_t n)
 {
-	long val = 0;
-	size_t i = 1;
+	size_t i = 0;
+
+	*val = 0;
+	while (i < MIN(n, 5)) {
+		/*
+		 * Least significant bytes are first, so we need to do this
+		 * nonsense.
+		 */
+		long tmp = bytes[i] & (i == 0 ? 0x3f : 0x7f);
+
+		if (i > 0) tmp <<= 6;
+		if (i > 1) tmp <<= 7*(i-1);
+		*val += tmp;
+
+		if (!(bytes[i] & (i == 0 ? 0x40 : 0x80))) {
+			i++;
+			break;
+		}
 
-	val += bytes[0] & 0x3f;
-	if (bytes[0] & 0x40) do {
-		val += bytes[i] & 0x7f;
-	} while (bytes[i] & 0x80 && i < 5);
+		i++;
+	}
 
-	return bytes[0] & 0x80 ? -val : val;
+	if (i > MIN(n, 5) || n == 0)
+		return 0;
+	if (bytes[0] & 0x80)
+		*val = -*val;
+	return i;
 }
 
 static struct upkg *init_upkg(unsigned char hdr[static UPKG_HDR_SIZE])
@@ -112,6 +144,72 @@ err:
 	return -1;
 }
 
+static int pkg_init_exports(struct upkg *pkg)
+{
+	size_t rc, len, nbuf = 0;
+	unsigned long index = 0;
+	char buf[512];
+
+	if (fseek(pkg->priv->f, pkg->priv->export_offset, SEEK_SET) != 0)
+		return -1;
+
+	pkg->priv->exports = malloc(pkg->export_count * sizeof *pkg->priv->exports);
+	if (!pkg->priv->exports)
+		return -1;
+
+	while (index < pkg->export_count) {
+		struct upkg_export *export = &pkg->priv->exports[index];
+
+		/* Read some data into buffer. */
+		if (!feof(pkg->priv->f)) {
+			rc = fread(buf+nbuf, 1, sizeof buf-nbuf, pkg->priv->f);
+			if (rc == 0)
+				goto err;
+			nbuf += rc;
+		}
+
+		len = 0;
+		rc = decode_index(&export->class, buf+len, nbuf-len);
+		if (rc == 0) goto err;
+		len += rc;
+
+		rc = decode_index(&export->super, buf+len, nbuf-len);
+		if (rc == 0) goto err;
+		len += rc;
+
+		if (nbuf-len < 4) goto err;
+		export->package = unpack_32_le(buf+len);
+		len += 4;
+
+		rc = decode_index(&export->name, buf+len, nbuf-len);
+		if (rc == 0) goto err;
+		len += rc;
+
+		if (nbuf-len < 4) goto err;
+		export->flags = unpack_32_le(buf+len);
+		len += 4;
+
+		rc = decode_index(&export->size, buf+len, nbuf-len);
+		if (rc == 0) goto err;
+		len += rc;
+
+		if (export->size) {
+			rc = decode_index(&export->offset, buf+len, nbuf-len);
+			if (rc == 0) goto err;
+			len += rc;
+		}
+
+		nbuf -= len;
+		memmove(buf, buf+len, nbuf);
+		index++;
+	}
+
+	return 0;
+err:
+	free(pkg->priv->exports);
+	return -1;
+}
+
 struct upkg *upkg_fopen(const char *path)
 {
 	unsigned char hdr_buf[UPKG_HDR_SIZE];
@@ -135,11 +233,17 @@ struct upkg *upkg_fopen(const char *path)
 	}
 	pkg->priv->f = f;
 
-	if (pkg_init_names(pkg) != 0) {
+	if (pkg_init_exports(pkg) != 0) {
 		goto err2;
 	}
 
+	if (pkg_init_names(pkg) != 0) {
+		goto err3;
+	}
+
 	return pkg;
+err3:
+	free(pkg->priv->exports);
 err2:
 	free(pkg->priv);
 	free(pkg);
@@ -158,11 +262,12 @@ int upkg_close(struct upkg *pkg)
 		for (unsigned i = 0; i < pkg->name_count; i++) {
 			free(pkg->priv->names[i].name);
 		}
-		free(pkg->priv->names);
 
 		return rc;
 	}
 
+	free(pkg->priv->exports);
+	free(pkg->priv->names);
 	free(pkg->priv);
 	free(pkg);
 
diff --git a/upkg.c b/upkg.c
index d7b181d..2694f5b 100644
--- a/upkg.c
+++ b/upkg.c
@@ -45,6 +45,8 @@ int main(int argc, char **argv)
 		printf("\t%s\n", upkg_get_name(pkg, i));
 	}
 
+	printf("Exports: %lu\n", pkg->export_count);
+
 	upkg_close(pkg);
 	return 0;
 }
-- 
2.43.2