// posix_fd.c - file descriptor table
#include "posix.h"
#include "posix_fd.h"
#include <syscall.h>

int errno = 0;

static FD_ENTRY gFdTable[FD_TABLE_PIDS][FD_MAX];

__declspec(dllexport) void PosixFdInit(void) {
    uint32_t pid = SysGetCurrentPid();
    uint32_t slot = pid % FD_TABLE_PIDS;

    // Clear this process's slice (handles inherited state from a previous
    // process that happened to land on the same slot - unlikely but safe).
    for (int i = 0; i < FD_MAX; i++)
        gFdTable[slot][i] = (FD_ENTRY){ FD_FREE, 0, false };

    gFdTable[slot][0] = (FD_ENTRY){ FD_CONSOLE_R, 0, true };
    gFdTable[slot][1] = (FD_ENTRY){ FD_CONSOLE_W, 0, true };
    gFdTable[slot][2] = (FD_ENTRY){ FD_CONSOLE_W, 0, true };
}

__declspec(dllexport) int FdAlloc(uint32_t pid, FD_TYPE type, uint32_t khandle) {
    uint32_t slot = pid % FD_TABLE_PIDS;
    for (int fd = 3; fd < FD_MAX; fd++) {
        if (!gFdTable[slot][fd].Used) {
            gFdTable[slot][fd] = (FD_ENTRY){ type, khandle, true };
            return fd;
        }
    }
    errno = EMFILE;
    return -1;
}

__declspec(dllexport) FD_ENTRY* FdGet(uint32_t pid, int fd) {
    if (fd < 0 || fd >= FD_MAX) { errno = EBADF; return (FD_ENTRY*)0; }
    uint32_t slot = pid % FD_TABLE_PIDS;
    FD_ENTRY* e = &gFdTable[slot][fd];
    if (!e->Used) { errno = EBADF; return (FD_ENTRY*)0; }
    return e;
}

__declspec(dllexport) void FdFree(uint32_t pid, int fd) {
    if (fd < 0 || fd >= FD_MAX) return;
    uint32_t slot = pid % FD_TABLE_PIDS;
    gFdTable[slot][fd] = (FD_ENTRY){ FD_FREE, 0, false };
}