#include <stdio.h>
#include <Windows.h>
#include <conio.h>

// To Compile: gcc enumprt.c -lwinspool -o enumprt.exe
// From: https://stackoverflow.com/questions/41147180/why-enumprintersa-and-enumprintersw-request-the-same-amount-of-memory

typedef BOOL (__stdcall *EnumPrintersAFuncPtr)(DWORD Flags, LPSTR Name, DWORD Level, LPBYTE pPrinterEnum, DWORD cbBuf, LPDWORD pcbNeeded, LPDWORD pcReturned);
typedef BOOL (__stdcall *EnumPrintersWFuncPtr)(DWORD Flags, LPWSTR Name, DWORD Level, LPBYTE pPrinterEnum, DWORD cbBuf, LPDWORD pcbNeeded, LPDWORD pcReturned);

void testFunc() {
    PPRINTER_INFO_4A ppi4a = NULL;
    PPRINTER_INFO_4W ppi4w = NULL;
    BOOL resa, resw;
    DWORD neededa = 0, returneda = 0, neededw = 0, returnedw = 0, gle = 0, i = 0, flags = PRINTER_ENUM_LOCAL;
    LPBYTE bufa = NULL, bufw = NULL;
    resa = EnumPrintersA(flags, NULL, 4, NULL, 0, &neededa, &returneda);
    if (resa) {
        printf("EnumPrintersA(1) succeeded with NULL buffer. Exiting...\n");
        return;
    } else {
        gle = GetLastError();
        if (gle != ERROR_INSUFFICIENT_BUFFER) {
            printf("EnumPrintersA(1) failed with %d(0x%08X) which is different than %d. Exiting...\n", gle, gle, ERROR_INSUFFICIENT_BUFFER);
            return;
        } else {
            printf("EnumPrintersA(1) needs a %d(0x%08X) bytes long buffer.\n", neededa, neededa);
        }
    }
    resw = EnumPrintersW(flags, NULL, 4, NULL, 0, &neededw, &returnedw);
    if (resw) {
        printf("EnumPrintersW(1) succeeded with NULL buffer. Exiting...\n");
        return;
    } else {
        gle = GetLastError();
        if (gle != ERROR_INSUFFICIENT_BUFFER) {
            printf("EnumPrintersW(1) failed with %d(0x%08X) which is different than %d. Exiting...\n", gle, gle, ERROR_INSUFFICIENT_BUFFER);
            return;
        } else {
            printf("EnumPrintersW(1) needs a %d(0x%08X) bytes long buffer.\n", neededw, neededw);
        }
    }

    bufa = (LPBYTE)calloc(1, neededa);
    if (bufa == NULL) {
        printf("calloc failed with %d(0x%08X). Exiting...\n", errno, errno);
        free(bufa);
        return;
    } else {
        printf("buffera[0x%08X:0x%08X]\n", (long)bufa, (long)bufa + neededa - 1);
    }
    bufw = (LPBYTE)calloc(1, neededw);
    if (bufw == NULL) {
        printf("calloc failed with %d(0x%08X). Exiting...\n", errno, errno);
        free(bufw);
        return;
    } else {
        printf("bufferw[0x%08X:0x%08X]\n", (long)bufw, (long)bufw + neededw - 1);
    }

    resa = EnumPrintersA(flags, NULL, 4, bufa, neededa, &neededa, &returneda);
    if (!resa) {
        gle = GetLastError();
        printf("EnumPrintersA(2) failed with %d(0x%08X). Exiting...\n", gle, gle);
        free(bufa);
        free(bufw);
        return;
    }
    printf("EnumPrintersA(2) copied %d bytes in the buffer out of which the first %d(0x%08X) represent %d structures of size %d\n", neededa, returneda * sizeof(PRINTER_INFO_4A), returneda * sizeof(PRINTER_INFO_4A), returneda, sizeof(PRINTER_INFO_4A));
    resw = EnumPrintersW(flags, NULL, 4, bufw, neededw, &neededw, &returnedw);
    if (!resw) {
        gle = GetLastError();
        printf("EnumPrintersW(2) failed with %d(0x%08X). Exiting...\n", gle, gle);
        free(bufw);
        free(bufa);
        return;
    }
    printf("EnumPrintersW(2) copied %d bytes in the buffer out of which the first %d(0x%08X) represent %d structures of size %d\n", neededw, returnedw * sizeof(PRINTER_INFO_4W), returnedw * sizeof(PRINTER_INFO_4W), returnedw, sizeof(PRINTER_INFO_4W));

    ppi4a = (PPRINTER_INFO_4A)bufa;
    ppi4w = (PPRINTER_INFO_4W)bufw;
    printf("\nPrinting ASCII results:\n");
    for (i = 0; i < returneda; i++) {
        printf("  Item %d\n    pPrinterName: [%s]\n", i, ppi4a[i].pPrinterName ? ppi4a[i].pPrinterName : "NULL");
    }
    printf("\nPrinting WIDE results:\n");
    for (i = 0; i < returnedw; i++) {
        wprintf(L"  Item %d\n    pPrinterName: [%s]\n", i, ppi4w[i].pPrinterName ? ppi4w[i].pPrinterName : L"NULL");
    }

    free(bufa);
    free(bufw);
}


int main() {
    testFunc();
    printf("\nPress a key to exit...\n");
    getch();
    return 0;
}