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POC++ Sending Image via HTTP
 

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    <p>I try to implement a simple HTTP server using C++. I was able to send text response to browser, but I am failing to send response for binary file request.</p> <p>Here is my code to get HTML response to PNG file request:</p> <pre><code>string create_html_output_for_binary(const string &amp;full_path) { const char* file_name = full_path.c_str(); FILE* file_stream = fopen(file_name, "rb"); string file_str; size_t file_size; if(file_stream != nullptr) { fseek(file_stream, 0, SEEK_END); long file_length = ftell(file_stream); rewind(file_stream); // Allocate memory. Info: http://www.cplusplus.com/reference/cstdio/fread/?kw=fread char* buffer = (char*) malloc(sizeof(char) * file_length); if(buffer != nullptr) { file_size = fread(buffer, 1, file_length, file_stream); stringstream out; for(int i = 0; i &lt; file_size; i++) { out &lt;&lt; buffer[i]; } string copy = out.str(); file_str = copy; } else { printf("buffer is null!"); } } else { printf("file_stream is null! file name -&gt; %s\n", file_name); } string html = "HTTP/1.1 200 Okay\r\nContent-Type: text/html; charset=ISO-8859-4 \r\n\r\n" + string("FILE NOT FOUND!!"); if(file_str.length() &gt; 0) { // HTTP/1.0 200 OK // Server: cchttpd/0.1.0 // Content-Type: image/gif // Content-Transfer-Encoding: binary // Content-Length: 41758 string file_size_str = to_string(file_str.length()); html = "HTTP/1.1 200 Okay\r\nContent-Type: image/png; Content-Transfer-Encoding: binary; Content-Length: " + file_size_str + ";charset=ISO-8859-4 \r\n\r\n" + file_str; printf("\n\nHTML -&gt; %s\n\nfile_str -&gt; %ld\n\n\n", html.c_str(), file_str.length()); } return html; } </code></pre> <p>This code successfully read file and store data on <code>char* buffer</code>. What makes me confuse is the <code>file_str</code> always contains <code>\211PNG</code>, although when I check its size, is much large than <code>\211PNG</code>. I suspect this is the problem that cause my image does not loaded in browsers because when I printf the html, it only shows:</p> <pre><code>HTTP/1.1 200 Okay Content-Type: image/png; Content-Transfer-Encoding: binary; Content-Length: 187542;charset=ISO-8859-4 \211PNG </code></pre> <p>What I am thinking is the way to send binary data to browser is same with sending text data, so I make the string header first, then read file data, convert it to string and combine with the header, then finally send a large single string to HTTP socket.</p> <p>I also tried this code:</p> <pre><code>if (file_stream != NULL) { short stringlength = 6; string mystring; mystring.reserve(stringlength); fseek(file_stream , 0, SEEK_SET); fread(&amp;mystring[0], sizeof(char), (size_t)stringlength, file_stream); printf("TEST -&gt; %s, length -&gt; %ld\n", mystring.c_str(), mystring.length()); fclose(file_stream ); } </code></pre> <p>But the HTML output always the same, and <code>mystring</code> also contains only <code>\211PNG</code> when printf-ed.</p> <p>Am I in the wrong path? Please help find out the mistakes in my code. Thank you.</p>
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    1. COIt looks like the PNG file contains a NULL character. printf's '%s' prints a char string until it encounters NULL and stops. Try using C++ streams instead: cout << mystring;
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    2. COYou should consider using `std::ifstream` and `std::ostream` rather than the C stream I/O calls.
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      1. USCaptain Obvlious
 

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