From 00f5f0706e7552e86a28d9fd66df962e095e8576 Mon Sep 17 00:00:00 2001
From: Nick Bowler <draconx@gmail.com>
Date: Sun, 23 Dec 2007 17:47:17 -0500
Subject: [PATCH] Add lbx_mopen() to allow "opening" a region of memory as an
 LBX archive.

---
 src/lbx.c | 120 ++++++++++++++++++++++++++++++++++++++++++++----------
 src/lbx.h |   1 +
 2 files changed, 100 insertions(+), 21 deletions(-)

diff --git a/src/lbx.c b/src/lbx.c
index 597d043..20c32e7 100644
--- a/src/lbx.c
+++ b/src/lbx.c
@@ -3,6 +3,7 @@
 #include <string.h>
 #include <stdint.h>
 #include <errno.h>
+#include <assert.h>
 
 #include "byteorder.h"
 #include "lbx.h"
@@ -15,6 +16,8 @@ int lbx_errno = 0;
 struct lbx_state {
 	const char *name;
 
+	unsigned char *mem;
+	size_t memsize;
 	FILE *f;
 	long foff;
 
@@ -70,6 +73,59 @@ readerr:
 	return NULL;
 }
 
+static int _lbx_memcpy(void *dest, struct lbx_state *src, size_t size)
+{
+	if (src->foff + size > src->memsize)
+		return -1;
+	memcpy(dest, src->mem + src->foff, size);
+	src->foff += size;
+	return 0;
+}
+
+struct lbx_state *lbx_mopen(void *_mem, size_t size, const char *name)
+{
+	struct lbx_state *new = NULL;
+	struct lbx_state tmp = { .mem = _mem, .memsize = size };
+	uint16_t nfiles, version;
+	uint32_t magic;
+
+	if (_lbx_memcpy(&nfiles,  &tmp, sizeof nfiles)  == -1) goto eof;
+	if (_lbx_memcpy(&magic,   &tmp, sizeof magic)   == -1) goto eof;
+	if (_lbx_memcpy(&version, &tmp, sizeof version) == -1) goto eof;
+
+	nfiles  = letohs(nfiles);
+	magic   = letohl(magic);
+	version = letohs(version);
+
+	if (magic != LBX_MAGIC) {
+		lbx_errno = LBX_EMAGIC;
+		return NULL;
+	}
+	
+	new = malloc(sizeof *new + (nfiles+1)*(sizeof *new->offsets));
+	if (!new) {
+		lbx_errno = -errno;
+		return NULL;
+	}
+	
+	*new = (struct lbx_state){
+		.name    = name,
+		.nfiles  = nfiles,
+		.mem     = _mem,
+		.memsize = size,
+		.foff    = tmp.foff,
+	};
+	
+	if (_lbx_memcpy(new->offsets, new, (nfiles+1)*(sizeof *new->offsets)))
+		goto eof;
+
+	return new;
+eof:
+	free(new);
+	lbx_errno = LBX_EEOF;
+	return NULL;
+}
+
 struct lbx_state *lbx_open(const char *path)
 {
 	struct lbx_state *new = NULL;
@@ -143,37 +199,41 @@ static int _lbx_fseek(struct lbx_state *lbx, size_t base)
 	return 0;
 }
 
-size_t lbx_extract(struct lbx_state *lbx, size_t index, FILE *of)
+static size_t
+_lbx_mextract(struct lbx_state *lbx, size_t base, size_t len, FILE *of)
+{
+	size_t rc;
+
+	assert(lbx->mem);
+	assert(base + len <= lbx->memsize);
+
+	rc = fwrite(lbx->mem + base, 1, len, of);
+	if (rc < len)
+		lbx_errno = -errno;
+
+	return rc;
+}
+
+static size_t
+_lbx_fextract(struct lbx_state *lbx, size_t base, size_t len, FILE *of)
 {
 	unsigned char buf[1024];
-	size_t rc, written = 0, base, len;
+	size_t rc, written = 0;
 
-	if (index >= lbx->nfiles) {
-		lbx_errno = LBX_ERANGE;
-		return 0;
-	}
-	
-	base = lbx->offsets[index];
-	len  = lbx->offsets[index+1] - lbx->offsets[index];
+	assert(lbx->f);
 
-	if (_lbx_fseek(lbx, base) == -1) {
-		/* lbx_errno set by _lbx_fseek(). */
+	if (_lbx_fseek(lbx, base) == -1)
 		return 0;
-	}
-
-	/* Copy file data */
+	
 	while (len) {
-		size_t amt = MIN(sizeof buf, len);
+		size_t amt = MIN(len, sizeof buf);
 
 		rc = fread(buf, 1, amt, lbx->f);
 		lbx->foff += rc;
 		len -= rc;
 		if (rc < amt) {
-			if (feof(lbx->f)) {
-				lbx_errno = LBX_EEOF;
-			} else {
-				lbx_errno = -errno;
-			}
+			if (feof(lbx->f)) lbx_errno = LBX_EEOF;
+			else lbx_errno = -errno;
 			break;
 		}
 
@@ -188,11 +248,29 @@ size_t lbx_extract(struct lbx_state *lbx, size_t index, FILE *of)
 	return written;
 }
 
+size_t lbx_extract(struct lbx_state *lbx, size_t index, FILE *of)
+{
+	size_t base, len;
+
+	if (index >= lbx->nfiles) {
+		lbx_errno = LBX_ERANGE;
+		return 0;
+	}
+	
+	base = lbx->offsets[index];
+	len  = lbx->offsets[index+1] - lbx->offsets[index];
+
+	if (lbx->mem)
+		return _lbx_mextract(lbx, base, len, of);
+	return _lbx_fextract(lbx, base, len, of);
+}
+
 void lbx_close(struct lbx_state *lbx)
 {
 	if (!lbx) return;
 
-	fclose(lbx->f);
+	if (lbx->f)
+		fclose(lbx->f);
 	free(lbx);
 }
 
diff --git a/src/lbx.h b/src/lbx.h
index 19848d2..92c533b 100644
--- a/src/lbx.h
+++ b/src/lbx.h
@@ -22,6 +22,7 @@ struct lbx_statbuf {
 
 /* Archive operations */
 LBX   *lbx_fopen(FILE *, const char *);
+LBX   *lbx_mopen(void *, size_t, const char *);
 LBX   *lbx_open(const char *);
 void   lbx_close(LBX *);
 size_t lbx_numfiles(LBX *);
-- 
2.43.2