add dup() function

[diamant3]

Tested only on PPSSPP

#include <pspkernel.h>
#include <pspdebug.h>

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

PSP_MODULE_INFO("dup_test", 0, 1, 0);
PSP_MAIN_THREAD_ATTR(THREAD_ATTR_USER);

#define printf pspDebugScreenPrintf

#define TEST_ASSERT(cond, msg)                 \
    do {                                       \
        if (cond)                              \
            printf("[PASS] %s\n", msg);        \
        else {                                 \
            printf("[FAIL] %s\n", msg);        \
            printf("       errno=%d (%s)\n",   \
                   errno, strerror(errno));    \
        }                                      \
    } while(0)

int exit_callback(int arg1, int arg2, void *common)
{
    sceKernelExitGame();
    return 0;
}


int CallbackThread(SceSize args, void *argp)
{
    int cbid = sceKernelCreateCallback(
        "Exit Callback",
        exit_callback,
        NULL);

    sceKernelRegisterExitCallback(cbid);

    sceKernelSleepThreadCB();

    return 0;
}


int main()
{
    pspDebugScreenInit();

    int fd_orig = open("test_dup.txt", O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (fd_orig < 0) {
        perror("Failed to open file");
        return 1;
    }

    int fd_copy = dup(fd_orig);
    if (fd_copy < 0) {
        perror("dup() failed");
        close(fd_orig);
        return 1;
    }
    printf("Original FD: %d, Duplicated FD: %d\n", fd_orig, fd_copy);

    const char *msg1 = "Hello ";
    write(fd_orig, msg1, strlen(msg1));

    const char *msg2 = "World!\n";
    write(fd_copy, msg2, strlen(msg2));


    close(fd_orig);
    close(fd_copy);
    
    printf("Test complete. Check 'test_dup.txt' for 'Hello World!'\n");

    sceKernelSleepThread();

    return 0;
}

[bucanero]

I'd keep this change as draft until it can be verified and working on real hardware