diff options
Diffstat (limited to 'libs/cairo-1.16.0/doc/public/html/bindings-streams.html')
| -rw-r--r-- | libs/cairo-1.16.0/doc/public/html/bindings-streams.html | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/libs/cairo-1.16.0/doc/public/html/bindings-streams.html b/libs/cairo-1.16.0/doc/public/html/bindings-streams.html new file mode 100644 index 0000000..ab8d3fc --- /dev/null +++ b/libs/cairo-1.16.0/doc/public/html/bindings-streams.html @@ -0,0 +1,91 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> +<title>Streams and File I/O: Cairo: A Vector Graphics Library</title> +<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> +<link rel="home" href="index.html" title="Cairo: A Vector Graphics Library"> +<link rel="up" href="language-bindings.html" title="Appendix A. Creating a language binding for cairo"> +<link rel="prev" href="bindings-overloading.html" title="Overloading and optional arguments"> +<link rel="next" href="bindings-errors.html" title="Error handling"> +<meta name="generator" content="GTK-Doc V1.27 (XML mode)"> +<link rel="stylesheet" href="style.css" type="text/css"> +</head> +<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> +<table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="5"><tr valign="middle"> +<td width="100%" align="left" class="shortcuts"></td> +<td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td> +<td><a accesskey="u" href="language-bindings.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td> +<td><a accesskey="p" href="bindings-overloading.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td> +<td><a accesskey="n" href="bindings-errors.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td> +</tr></table> +<div class="sect1"> +<div class="titlepage"><div><div><h2 class="title" style="clear: both"> +<a name="bindings-streams"></a>Streams and File I/O</h2></div></div></div> +<p> + Various places in the cairo API deal with reading and writing + data, whether from and to files, or to other sources and + destinations. In these cases, what is typically provided in the + C API is a simple version that just takes a filename, and a + complex version that takes a callback function. + An example is the PNG handling functions: + </p> +<pre class="programlisting"> +cairo_surface_t * +cairo_image_surface_create_from_png (const char *filename); + +cairo_surface_t * +cairo_image_surface_create_from_png_stream (cairo_read_func_t read_func, + void *closure); + +cairo_status_t +cairo_surface_write_to_png (cairo_surface_t *surface, + const char *filename); + +cairo_status_t +cairo_surface_write_to_png_stream (cairo_surface_t *surface, + cairo_write_func_t write_func, + void *closure);</pre> +<p> + The expectation is that the filename version will be mapped + literally in the language binding, but the callback version + will be mapped to a version that takes a language stream + object. For example, in Java, the four functions above + might be mapped to: + </p> +<pre class="programlisting"> +static public ImageSurface createFromPNG (String filename) throws IOException; +static public ImageSurface createFromPNG (InputStream stream) throws IOException; +public void writeToPNG (String filename) throws IOException; +public void writeToPNG (OutputStream stream) throws IOException; +</pre> +<p> + In many cases, it will be better to + implement the filename version internally + using the stream version, rather than building it on top of the + filename version in C. The reason for this is that will + naturally give a more standard handling of file errors for + the language, as seen in the above Java example, where + <code class="methodname">createFromPNG()</code> is marked as raising + an exception. Propagating exceptions from inside the callback + function to the caller will pose a challenge to the language + binding implementor, since an exception must not propagate + through the Cairo code. A technique that will be useful in + some cases is to catch the exception in the callback, + store the exception object inside a structure pointed to by + <em class="parameter"><code>closure</code></em>, and then rethrow it once + the function returns. + </p> +<p class="remark"><em><span class="remark"> + I'm not sure how to handle this for + <a class="link" href="cairo-PDF-Surfaces.html#cairo-pdf-surface-create-for-stream" title="cairo_pdf_surface_create_for_stream ()"><code class="function">cairo_pdf_surface_create_for_stream()</code></a>. + Other than keep a “exception to rethrow” thread-specific + variable + that is checked after <span class="emphasis"><em>every</em></span> call to a Cairo + function. + </span></em></p> +</div> +<div class="footer"> +<hr>Generated by GTK-Doc V1.27</div> +</body> +</html>
\ No newline at end of file |