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POCasting from unsigned into signed char in C
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copied!<p>I am converting an input <code>raw pcm</code> stream into <code>mp3</code> using <code>lame</code>. The encoding function within that library returns <code>mp3</code> encoded samples in an array of type <code>unsigned char</code>. This mp3-encoded stream now needs to be placed within an <code>flv</code> container which uses a function that writes encoded samples in <code>char</code> array. My problem is that I am passing the array from <code>lame</code> (of type <code>unsigned char</code>) into the <code>flv</code> library. The following piece of code (only symbolic) illustrates my problem: </p> <pre><code>/* cast from unsigned char to char. */ #include <stdio.h> #include <stdlib.h> void display(char *buff, int len) { int i = 0; for(i = 0; i < len; i++) { printf("buff[%d] = %c\n", i, buff[i]); } } int main() { int len = 10; unsigned char* buff = (unsigned char*) malloc(len * sizeof(unsigned char)); int i = 0; for(i = 65; i < (len + 65); i++) { buff[i] = (unsigned char) i; printf("char = %c", (char) i); } printf("Displaying array in main.\n"); for(i = 0; i < len; i++) { printf("buff[%d] = %u\n", i, 'buff[i]'); } printf("Displaying array in func.\n"); display(buff, len); return 0; } </code></pre> <p>My question(s):<br> 1. Is the implicit type conversion in the code below (as demonstrated by passing of <code>buff</code> into function <code>display</code> safe? Is some weird behaviour likely to occur?<br> 2. Given that I have little option but to stick to the functions as they are present, is there a "safe" way of converting an array of <code>unsigned char</code>s into <code>char</code>s?</p>

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