[2/4] qemu-img: dd: add isize parameter

Commit Message

Fiona Ebner Feb. 10, 2022, 1:31 p.m. UTC

From: Wolfgang Bumiller <[e-mail]>

for writing small images from stdin to bigger ones.

In order to distinguish between an actually unexpected and
an expected end of input.

Signed-off-by: Wolfgang Bumiller <[e-mail]>
Signed-off-by: Thomas Lamprecht <[e-mail]>
[FE: override size earlier
     use flag to detect parameter
     add documenation]
Signed-off-by: Fabian Ebner <[e-mail]>
---
 docs/tools/qemu-img.rst | 10 ++++++++--
 qemu-img-cmds.hx        |  4 ++--
 qemu-img.c              | 24 +++++++++++++++++++++++-
 3 files changed, 33 insertions(+), 5 deletions(-)

Patch

diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst
index 775eaf3097..43328fe108 100644
--- a/docs/tools/qemu-img.rst
+++ b/docs/tools/qemu-img.rst
@@ -230,6 +230,10 @@  Parameters to dd subcommand:
 
   Sets the number of input blocks to skip
 
+.. option:: isize=INPUT_SIZE
+
+  Treat the input image or stream as if it had this size
+
 .. option:: osize=OUTPUT_SIZE
 
   Sets the output image's size
@@ -492,7 +496,7 @@  Command description:
   it doesn't need to be specified separately in this case.
 
 
-.. option:: dd [--image-opts] [-U] [-f FMT] [-O OUTPUT_FMT] [bs=BLOCK_SIZE] [count=BLOCKS] [skip=BLOCKS] [osize=OUTPUT_SIZE] [if=INPUT] [of=OUTPUT]
+.. option:: dd [--image-opts] [-U] [-f FMT] [-O OUTPUT_FMT] [bs=BLOCK_SIZE] [count=BLOCKS] [skip=BLOCKS] [isize=INPUT_SIZE] [osize=OUTPUT_SIZE] [if=INPUT] [of=OUTPUT]
 
   dd copies from *INPUT* file (default: STDIN) to *OUTPUT* file (default:
   STDOUT) converting it from *FMT* format to *OUTPUT_FMT* format.
@@ -504,7 +508,9 @@  Command description:
   The size syntax is similar to :manpage:`dd(1)`'s size syntax.
 
   The output image will be created with size *OUTPUT_SIZE* and at most this many
-  bytes will be copied.
+  bytes will be copied. When *INPUT_SIZE* is positive, it overrides the input
+  image's size for the copy operation. When *INPUT_SIZE* is zero and reading
+  from STDIN, do not treat premature end of the input stream as an error.
 
 .. option:: info [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [--backing-chain] [-U] FILENAME
 
diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index e4935365c9..50993e6c47 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -58,9 +58,9 @@  SRST
 ERST
 
 DEF("dd", img_dd,
-    "dd [--image-opts] [-U] [-f fmt] [-O output_fmt] [bs=block_size] [count=blocks] [skip=blocks] [osize=output_size] [if=input] [of=output]")
+    "dd [--image-opts] [-U] [-f fmt] [-O output_fmt] [bs=block_size] [count=blocks] [skip=blocks] [isize=input_size] [osize=output_size] [if=input] [of=output]")
 SRST
-.. option:: dd [--image-opts] [-U] [-f FMT] [-O OUTPUT_FMT] [bs=BLOCK_SIZE] [count=BLOCKS] [skip=BLOCKS] [osize=OUTPUT_SIZE] [if=INPUT] [of=OUTPUT]
+.. option:: dd [--image-opts] [-U] [-f FMT] [-O OUTPUT_FMT] [bs=BLOCK_SIZE] [count=BLOCKS] [skip=BLOCKS] [isize=INPUT_SIZE] [osize=OUTPUT_SIZE] [if=INPUT] [of=OUTPUT]
 ERST
 
 DEF("info", img_info,
diff --git a/qemu-img.c b/qemu-img.c
index ea488fd190..630928773d 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -4820,11 +4820,13 @@  static int img_bitmap(int argc, char **argv)
 #define C_OF      010
 #define C_SKIP    020
 #define C_OSIZE   040
+#define C_ISIZE   0100
 
 struct DdInfo {
     unsigned int flags;
     int64_t count;
     int64_t osize;
+    int64_t isize;
 };
 
 struct DdIo {
@@ -4913,6 +4915,19 @@  static int img_dd_osize(const char *arg,
     return 0;
 }
 
+static int img_dd_isize(const char *arg,
+                        struct DdIo *in, struct DdIo *out,
+                        struct DdInfo *dd)
+{
+    dd->isize = cvtnum("isize", arg);
+
+    if (dd->isize < 0) {
+        return 1;
+    }
+
+    return 0;
+}
+
 static int img_dd(int argc, char **argv)
 {
     int ret = 0;
@@ -4934,6 +4949,7 @@  static int img_dd(int argc, char **argv)
         .flags = 0,
         .count = 0,
         .osize = 0,
+        .isize = 0,
     };
     struct DdIo in = {
         .bsz = 512, /* Block size is by default 512 bytes */
@@ -4955,6 +4971,7 @@  static int img_dd(int argc, char **argv)
         { "of", img_dd_of, C_OF },
         { "skip", img_dd_skip, C_SKIP },
         { "osize", img_dd_osize, C_OSIZE },
+        { "isize", img_dd_isize, C_ISIZE },
         { NULL, NULL, 0 }
     };
     const struct option long_options[] = {
@@ -5061,7 +5078,9 @@  static int img_dd(int argc, char **argv)
         }
     }
 
-    if (dd.flags & C_IF) {
+    if (dd.flags & C_ISIZE && dd.isize > 0) {
+        size = dd.isize;
+    } else if (dd.flags & C_IF) {
         size = blk_getlength(blk1);
         if (size < 0) {
             error_report("Failed to get size for '%s'", in.filename);
@@ -5174,6 +5193,9 @@  static int img_dd(int argc, char **argv)
         } else {
             in_ret = read(STDIN_FILENO, in.buf, in_bsz);
             if (in_ret == 0) {
+                if (dd.flags & C_ISIZE && dd.isize == 0) {
+                    goto out;
+                }
                 /* early EOF is considered an error */
                 error_report("Input ended unexpectedly");
                 ret = -1;