Author: wyoung
Date: Tue May 18 05:17:23 2010
New Revision: 2646
URL: http://svn.gna.org/viewcvs/mysqlpp?rev=2646&view=rev
Log:
Code clarity improvements to examples/load_jpeg
Modified:
trunk/examples/images.h
trunk/examples/load_jpeg.cpp
Modified: trunk/examples/images.h
URL:
http://svn.gna.org/viewcvs/mysqlpp/trunk/examples/images.h?rev=2646&r1=2645&r2=2646&view=diff
==============================================================================
--- trunk/examples/images.h (original)
+++ trunk/examples/images.h Tue May 18 05:17:23 2010
@@ -1,7 +1,7 @@
/***********************************************************************
images.h - Declares the images table SSQLS.
- Copyright (c) 2008 by Educational Technology Resources, Inc.
+ Copyright (c) 2008-2010 by Educational Technology Resources, Inc.
Others may also hold copyrights on code in this file. See the
CREDITS.txt file in the top directory of the distribution for details.
@@ -28,5 +28,5 @@
sql_create_2(images,
1, 2,
- mysqlpp::Null<mysqlpp::sql_int_unsigned>, id,
- mysqlpp::Null<mysqlpp::sql_blob>, data)
+ mysqlpp::sql_int_unsigned_null, id,
+ mysqlpp::sql_blob_null, data)
Modified: trunk/examples/load_jpeg.cpp
URL:
http://svn.gna.org/viewcvs/mysqlpp/trunk/examples/load_jpeg.cpp?rev=2646&r1=2645&r2=2646&view=diff
==============================================================================
--- trunk/examples/load_jpeg.cpp (original)
+++ trunk/examples/load_jpeg.cpp Tue May 18 05:17:23 2010
@@ -36,19 +36,37 @@
// This is just an implementation detail for the example. Skip down to
-// main() for the concept this example is trying to demonstrate.
+// main() for the concept this example is trying to demonstrate. You
+// can simply assume that, given a BLOB containing a valid JPEG, it
+// returns true.
static bool
-is_jpeg(const char* img_data)
+is_jpeg(const mysqlpp::sql_blob& img, const char** whynot)
{
+ // See http://stackoverflow.com/questions/2253404/ for
+ // justification for the various tests.
const unsigned char* idp =
- reinterpret_cast<const unsigned char*>(img_data);
- return (idp[0] == 0xFF) && (idp[1] == 0xD8) &&
- ((memcmp(idp + 6, "JFIF", 4) == 0) ||
- (memcmp(idp + 6, "Exif", 4) == 0));
+ reinterpret_cast<const unsigned char*>(img.data());
+ if (img.size() < 125) {
+ *whynot = "a valid JPEG must be at least 125 bytes";
+ }
+ else if ((idp[0] != 0xFF) || (idp[1] != 0xD8)) {
+ *whynot = "file does not begin with JPEG sigil bytes";
+ }
+ else if ((memcmp(idp + 6, "JFIF", 4) != 0) &&
+ (memcmp(idp + 6, "Exif", 4) != 0)) {
+ *whynot = "file does not contain JPEG type word";
+ }
+ else {
+ *whynot = 0;
+ return true;
+ }
+
+ return false;
}
-// Another implementation detail. Skip to main().
+// Skip to main() before studying this. This is a little too
+// low-level to bother with on your first pass thru the code.
static bool
load_jpeg_file(const mysqlpp::examples::CommandLine& cmdline,
images& img, string& img_name)
@@ -62,35 +80,24 @@
img_name = cmdline.extra_args()[0];
ifstream img_file(img_name.c_str(), ios::ate | ios::binary);
if (img_file) {
- // File opened, so try to slurp its contents into RAM. The key
- // thing to get from this function is that we're storing the
- // binary data in a mysqlpp::sql_blob value, which we assign
from
- // a C++ string (stringstream::str()), thus not truncating the
- // string at the first embedded null character.
- stringstream sstr;
- sstr << img_file.rdbuf();
- img.data.data = sstr.str();
+ // File opened, so try to slurp its contents into RAM. (See
+ // http://stackoverflow.com/questions/116038/) for explanation.)
+ //
+ // The key thing to get from this function is that we're storing
+ // the binary data in a mysqlpp::sql_blob value, which we assign
+ // from a C++ string (stringstream::str()), thus not truncating
+ // the string at the first embedded null character.
+ img.data.data = static_cast<const stringstream*>(
+ &(stringstream() << img_file.rdbuf()))->str();
// Check JPEG data for sanity.
- //
- // All these 'data's sure do look foolish, don't they? Sorry,
- // we're not trying to be obscure here, it's just a coincidence
- // of naming. The triple 'data' in the is_jpeg() call breaks
- // down like this:
- //
- // 1. We're accessing to the JPEG BLOB column, images.data.
- // 2. We then dig down to the mysqlpp::sql_blob object through
- // its mysqlpp::Null<> wrapper, which we need to allow a
- // "NULL JPEG" in the DB when the file doesn't exist.
- // 3. Finally, we need to pass a raw, unterminated char buffer
- // pointer to is_jpeg(), which mysqlpp::sql_blob::data()
- // returns, mirroring C++ std::string interface.
- if ((img.data.data.size() > 10) &&
- is_jpeg(img.data.data.data())) {
+ const char* error;
+ if (is_jpeg(img.data.data, &error)) {
return true;
}
else {
- cerr << '"' << img_file << "\" isn't a JPEG file!" <<
endl;
+ cerr << '"' << img_name << "\" isn't a JPEG: " <<
+ error << '!' << endl;
}
}
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