Author: mysqlpp
Date: Thu Nov 26 21:06:58 2009
New Revision: 2584
URL: http://svn.gna.org/viewcvs/mysqlpp?rev=2584&view=rev
Log:
Reworked the load_jpeg example code for clarity, extracting
load_jpeg_file() routine as an implementation detail and making that use
the C++ stringstream "slurp into string" idiom instead of allocating a C
char buffer and copying that into a std::string.
Modified:
trunk/examples/load_jpeg.cpp
Modified: trunk/examples/load_jpeg.cpp
URL:
http://svn.gna.org/viewcvs/mysqlpp/trunk/examples/load_jpeg.cpp?rev=2584&r1=2583&r2=2584&view=diff
==============================================================================
--- trunk/examples/load_jpeg.cpp (original)
+++ trunk/examples/load_jpeg.cpp Thu Nov 26 21:06:58 2009
@@ -35,6 +35,8 @@
using namespace mysqlpp;
+// This is just an implementation detail for the example. Skip down to
+// main() for the concept this example is trying to demonstrate.
static bool
is_jpeg(const char* img_data)
{
@@ -43,6 +45,62 @@
return (idp[0] == 0xFF) && (idp[1] == 0xD8) &&
((memcmp(idp + 6, "JFIF", 4) == 0) ||
(memcmp(idp + 6, "Exif", 4) == 0));
+}
+
+
+// Another implementation detail. Skip to main().
+static bool
+load_jpeg_file(const mysqlpp::examples::CommandLine& cmdline,
+ images& img, string& img_name)
+{
+ if (cmdline.extra_args().size() == 0) {
+ // Nothing for us to do here. Caller will insert NULL BLOB.
+ return true;
+ }
+
+ // Got a file's name on the command line, so open it.
+ 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();
+
+ // Check JPEG data for sanity
+ if (img.data.data.size() > 10) {
+ // The following triple 'data' sure does look foolish,
+ // doesn't it? Sorry, we're not trying to be obscure
here,
+ // it's just a coincidence of naming. Right-to-left,
what
+ // we have here is:
+ //
+ // 1. A call to mysqlpp::sql_blob::data() (mirroring
C++'s
+ // std::string:data() interface) to get the raw C
data
+ // pointer without null-terminating it first.
+ // 2. Access to the mysqlpp::sql_blob object through its
+ // mysqlpp::Null<> wrapper, which lets us have a
"NULL
+ // JPEG" in the DB when the file doesn't exist.
+ // 3. Access to the JPEG BLOB column, images.data.
+ if (is_jpeg(img.data.data.data())) {
+ return true;
+ }
+ else {
+ cerr << '"' << img_file <<
+ "\" isn't a JPEG!" << endl;
+ cmdline.print_usage("[jpeg_file]");
+ return false;
+ }
+ }
+ else {
+ cerr << "File is too short to be a JPEG!" << endl;
+ cmdline.print_usage("[jpeg_file]");
+ return false;
+ }
+ }
}
@@ -60,58 +118,27 @@
mysqlpp::Connection con(mysqlpp::examples::db_name,
cmdline.server(), cmdline.user(),
cmdline.pass());
- // Try to create a new item in the images table, based on what
- // we got on the command line.
+ // Load the file named on the command line
images img(mysqlpp::null, mysqlpp::null);
- string img_name = "NULL";
- if (cmdline.extra_args().size()) {
- // We received at least one non-option argument on the
- // command line, so treat it as a file name
- img_name = cmdline.extra_args()[0];
- ifstream img_file(img_name.c_str(), ios::ate |
ios::binary);
- if (img_file) {
- size_t img_size = img_file.tellg();
- if (img_size > 10) {
- img_file.seekg(0, ios::beg);
- char* img_buffer = new char[img_size];
- img_file.read(img_buffer, img_size);
- if (is_jpeg(img_buffer)) {
- img.data =
mysqlpp::sql_blob(img_buffer, img_size);
- }
- else {
- cerr << '"' << img_file <<
- "\" isn't a
JPEG!" << endl;
- }
- delete[] img_buffer;
- }
- else {
- cerr << "File is too short to be a
JPEG!" << endl;
- }
- }
+ string img_name("NULL");
+ if (load_jpeg_file(cmdline, img, img_name)) {
+ // Insert image data or SQL NULL into the images.data
BLOB
+ // column. The key here is that we're holding the raw
+ // binary data in a mysqlpp::sql_blob, which avoids data
+ // conversion problems that can lead to treating BLOB
data
+ // as C strings, thus causing null-truncation. The fact
+ // that we're using SSQLS here is a side issue, simply
+ // demonstrating that mysqlpp::Null<mysqlpp::sql_blob>
is
+ // now legal in SSQLS, as of MySQL++ 3.0.7.
+ Query query = con.query();
+ query.insert(img);
+ SimpleResult res = query.execute();
- if (img.data.data.empty()) {
- // File name was bad, or file contents aren't
JPEG.
- cmdline.print_usage("[jpeg_file]");
- return 1;
- }
+ // Report successful insertion
+ cout << "Inserted \"" << img_name <<
+ "\" into images table, " <<
img.data.data.size() <<
+ " bytes, ID " << res.insert_id() <<
endl;
}
- // else, no image given on command line, so insert SQL NULL
- // instead of image data. NULL BLOB columns in SSQLS is
- // legal as of MySQL++ v3.0.7.
-
- // Insert image data or SQL NULL into the images.data BLOB
- // column. By inserting it as an SSQLS with a mysqlpp::sql_blob
- // member, we avoid truncating it at the first embedded C null
- // character ('\0'), as would happen if we used the raw
- // character buffer we allocated above.
- Query query = con.query();
- query.insert(img);
- SimpleResult res = query.execute();
-
- // Report successful insertion
- cout << "Inserted \"" << img_name <<
- "\" into images table, " <<
img.data.data.size() <<
- " bytes, ID " << res.insert_id() << endl;
}
catch (const BadQuery& er) {
// Handle any query errors
_______________________________________________
Mysqlpp-commits mailing list
[email protected]
https://mail.gna.org/listinfo/mysqlpp-commits
