snprintf for decomp

/*
 * This is free and unencumbered software released into the public domain.
 *
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 *
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * For more information, please refer to <http://unlicense.org>
 */

#include "global.h"

// Add these two to a header
s32 vsnprintf(char* dst, u32 size, const char* fmt, va_list args);
s32 snprintf(char* dst, u32 size, const char* fmt, ...);

typedef struct {
    char* dst;    // current dst
    char* dstEnd; // end dst
} NPrintf;

static void* proutNSprintf(void* arg, const char* str, u32 size) {
    NPrintf* np = (NPrintf*)arg;

    if (np->dst >= np->dstEnd || np->dst == NULL) {
        // reached or passed the end, don't write out but continue
        // in order to get the full string length
        return np;
    }
    // ensure size does not end up out of bounds
    size = MIN(size, np->dstEnd - np->dst);
    np->dst = (char*)memcpy(np->dst, str, size) + size;
    return np;
}

s32 vsnprintf(char* dst, u32 size, const char* fmt, va_list args) {
    NPrintf np;
    s32 len;

    // dst can be null
    np.dst = dst;
    // size can be zero
    np.dstEnd = &dst[MAX(size - 1, 0)];

    len = _Printf(proutNSprintf, &np, fmt, args);
    if (dst != NULL && size > 0 && len > -1) {
        // calculated length may not always be in the buffer,
        // so terminate at min of the two
        dst[MIN(len, size - 1)] = '\0';
    }
    return len;
}

s32 snprintf(char* dst, u32 size, const char* fmt, ...) {
    s32 len;
    va_list args;
    va_start(args, fmt);

    len = vsnprintf(dst, size, fmt, args);

    va_end(args);
    return len;
}