Add openmem() function to read from memory as if it were a file

Reading from memory as if it were a file is pretty easy... we just
treat it as a really big block buffer and tell the file layer that we
already closed the underlying handle.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

4 files changed, 70 insertions, 9 deletions

diff --git a/com32/include/dev.h b/com32/include/dev.h
index 7809fb56..70b3165c 100644
--- a/com32/include/dev.h
+++ b/com32/include/dev.h
@@ -41,6 +41,7 @@ struct input_dev;
 struct output_dev;
 
 __extern int opendev(const struct input_dev *, const struct output_dev *, int);
+__extern int openmem(const void *, size_t, int);
 
 /* Common generic devices */
 
diff --git a/com32/lib/sys/file.h b/com32/lib/sys/file.h
index fff91b19..66192fbf 100644
--- a/com32/lib/sys/file.h
+++ b/com32/lib/sys/file.h
@@ -56,18 +56,18 @@ struct input_dev {
     uint16_t dev_magic;		/* Magic number */
     uint16_t flags;		/* Flags */
     int fileflags;		/* Permitted file flags */
-     ssize_t(*read) (struct file_info *, void *, size_t);
-    int (*close) (struct file_info *);
-    int (*open) (struct file_info *);
+    ssize_t (*read)(struct file_info *, void *, size_t);
+    int (*close)(struct file_info *);
+    int (*open)(struct file_info *);
 };
 
 struct output_dev {
     uint16_t dev_magic;		/* Magic number */
     uint16_t flags;		/* Flags */
     int fileflags;
-     ssize_t(*write) (struct file_info *, const void *, size_t);
-    int (*close) (struct file_info *);
-    int (*open) (struct file_info *);
+    ssize_t (*write)(struct file_info *, const void *, size_t);
+    int (*close)(struct file_info *);
+    int (*open)(struct file_info *);
     const struct output_dev *fallback;	/* Fallback option for certain consoles */
 };
 
diff --git a/com32/lib/sys/open.c b/com32/lib/sys/open.c
index aabbec21..114728ec 100644
--- a/com32/lib/sys/open.c
+++ b/com32/lib/sys/open.c
@@ -41,7 +41,7 @@
 extern ssize_t __file_read(struct file_info *, void *, size_t);
 extern int __file_close(struct file_info *);
 
-static const struct input_dev file_dev = {
+const struct input_dev __file_dev = {
     .dev_magic = __DEV_MAGIC,
     .flags = __DEV_FILE | __DEV_INPUT,
     .fileflags = O_RDONLY,
@@ -56,7 +56,7 @@ int open(const char *pathname, int flags, ...)
     int fd;
     struct file_info *fp;
 
-    fd = opendev(&file_dev, NULL, flags);
+    fd = opendev(&__file_dev, NULL, flags);
 
     if (fd < 0)
 	return -1;
@@ -78,7 +78,7 @@ int open(const char *pathname, int flags, ...)
 
     {
 	uint16_t blklg2;
-asm("bsrw %1,%0": "=r"(blklg2):"rm"(regs.ecx.w[0]));
+	asm("bsrw %1,%0" : "=r"(blklg2) : "rm"(regs.ecx.w[0]));
 	fp->i.blocklg2 = blklg2;
     }
     fp->i.length = regs.eax.l;
diff --git a/com32/lib/sys/openmem.c b/com32/lib/sys/openmem.c
new file mode 100644
index 00000000..13a45c2a
--- /dev/null
+++ b/com32/lib/sys/openmem.c
@@ -0,0 +1,60 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 2003-2008 H. Peter Anvin - All Rights Reserved
+ *
+ *   Permission is hereby granted, free of charge, to any person
+ *   obtaining a copy of this software and associated documentation
+ *   files (the "Software"), to deal in the Software without
+ *   restriction, including without limitation the rights to use,
+ *   copy, modify, merge, publish, distribute, sublicense, and/or
+ *   sell copies of the Software, and to permit persons to whom
+ *   the Software is furnished to do so, subject to the following
+ *   conditions:
+ *
+ *   The above copyright notice and this permission notice shall
+ *   be included in all copies or substantial portions of the Software.
+ *
+ *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ *   OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * ----------------------------------------------------------------------- */
+
+#include <errno.h>
+#include <com32.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include "file.h"
+
+/*
+ * openmem.c
+ *
+ * Open a chunk of memory as if it was a file
+ */
+
+const struct input_dev __file_dev;
+
+int openmem(const void *base, size_t len, int flags)
+{
+    com32sys_t regs;
+    int fd;
+    struct file_info *fp;
+
+    fd = opendev(&__file_dev, NULL, flags);
+
+    if (fd < 0)
+	return -1;
+
+    fp->i.length  = fp->i.nbytes = len;
+    fp->i.datap   = (void *)base;
+    fp->i.filedes = 0;		/* No actual file */
+    fp->i.offset  = 0;
+
+    return fd;
+}