DOCUMENT:Q104644 29-NOV-2001 [visualc] TITLE :INFO: Passing C Arrays to MASM by Reference PRODUCT :Microsoft C Compiler PROD/VER::1.0,1.5,2.0,4.0,5.0,6.0,7.0 OPER/SYS: KEYWORDS:kbLangC kbVC100 kbVC150 kbVC200 kbVC400 kbVC500 kbVC600 ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft C for MS-DOS - Microsoft C for OS/2 - Microsoft C/C++ for MS-DOS, version 7.0 - Microsoft Visual C++, versions 1.0, 1.5, 2.0, 4.0 - Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0 - Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0 - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 ------------------------------------------------------------------------------- SUMMARY ======= The sample code below demonstrates how to pass C arrays of type char, short, and long to a Microsoft Macro Assembler (MASM) procedure by reference. MORE INFORMATION ================ The samples below include one C file and three different assembly files. The three assembly files demonstrate how to pass variables by reference in small model and large model for MS-DOS and in flat model for Windows NT. Link only the appropriate assembly module to the C module. Note that MASM 6.1 or later and the C/C++ 32-bit compiler that ships with Visual C++, 32-bit Edition, are required to build the flat model Windows NT version. Sample Code ----------- // Filename: CMAIN.C // Compile options needed: /c #include #ifdef __cplusplus extern "C" { #endif void MasmSub (char *, short *, long *); #ifdef __cplusplus } #endif char chararray[4] = "abc"; short shortarray[3] = {1, 2, 3}; long longarray[3] = {32768, 32769, 32770}; main () { printf ("%s\n", chararray); printf ("%d %d %d\n", shortarray[0], shortarray[1], shortarray[2]); printf ("%ld %ld %ld\n", longarray[0], longarray[1], longarray[2]); MasmSub (chararray, shortarray, longarray); printf ("%s\n", chararray); printf ("%d %d %d\n", shortarray[0], shortarray[1], shortarray[2]); printf ("%ld %ld %ld", longarray[0], longarray[1], longarray[2]); } Sample Code for MS-DOS Small Model Version ------------------------------------------ ; Filename: MASMSUB.ASM ; Assemble options needed for MASM: /MX ; Assemble options needed for ML: /c /Cx .MODEL small, C .286 .CODE MasmSub PROC uses si, \ arraychar:PTR, \ arrayshort:PTR, \ arraylong:PTR mov si, arraychar ; Load SI with the address of the char array. mov BYTE PTR [si], "x" ; Since a char is 1 byte long, each mov BYTE PTR [si+1], "y" ; successive element can be accessed mov BYTE PTR [si+2], "z" ; by adding 1 more to si. mov si, arrayshort ; Load SI with the address of the short array. add WORD PTR [si], 7 ; Since a short is 2 bytes long, each add WORD PTR [si+2], 7 ; successive element can be accessed add WORD PTR [si+4], 7 ; by adding 2 more to si. mov si, arraylong ; Load SI with the address of the long array. add WORD PTR [si], 1 ; Since a long is 4 bytes long, each adc WORD PTR [si+2], 0 ; successive element in the array add WORD PTR [si+4], 1 ; can be accessed by adding 4 more adc WORD PTR [si+6], 0 ; to si (or 4 more to si+2 to access add WORD PTR [si+8], 1 ; the high word of each element). adc WORD PTR [si+10], 0 ret MasmSub ENDP END Sample Code for MS-DOS Large Model Version ------------------------------------------ ; Filename: MASMSUB.ASM ; Assemble options needed for MASM: /MX ; Assemble options needed for ML: /c /Cx .MODEL large, C .286 .CODE MasmSub PROC uses es si, \ arraychar:PTR, \ arrayshort:PTR, \ arraylong:PTR les si, arraychar ; Load ES:SI with the address of the char array. mov BYTE PTR es:[si], "x" ; Since a char is 1 byte long, each mov BYTE PTR es:[si+1], "y" ; successive element can be accessed mov BYTE PTR es:[si+2], "z" ; by adding 1 more to si. les si, arrayshort ; Load ES:SI with the address of the short array. add WORD PTR es:[si], 7 ; Since a short is 2 bytes long, each add WORD PTR es:[si+2], 7 ; successive element can be accessed add WORD PTR es:[si+4], 7 ; by adding 2 more to si. les si, arraylong ; Load ES:SI with the address of the long array. add WORD PTR es:[si], 1 ; Since a long is 4 bytes long, each adc WORD PTR es:[si+2], 0 ; successive element in the array add WORD PTR es:[si+4], 1 ; can be accessed by adding 4 more adc WORD PTR es:[si+6], 0 ; to si (or 4 more to si+2 to access add WORD PTR es:[si+8], 1 ; the high word of each element). adc WORD PTR es:[si+10], 0 ret MasmSub ENDP END Sample Code for Windows NT Flat Model Version --------------------------------------------- ; Filename: MASMSUB.ASM ; Assemble options needed for ML: /c /Cx /coff .386 .MODEL flat, C .CODE MasmSub PROC uses esi, \ arraychar:PTR, \ arrayshort:PTR, \ arraylong:PTR mov esi, arraychar ; Load ESI with the address of the char array. mov BYTE PTR [esi], "x" ; Since a char is 1 byte long, each mov BYTE PTR [esi+1], "y" ; successive element can be accessed mov BYTE PTR [esi+2], "z" ; by adding 1 more to esi. mov esi, arrayshort; Load ESI with the address of the short array. add WORD PTR [esi], 7 ; Since a short is 2 bytes long, each add WORD PTR [esi+2], 7 ; successive element can be accessed add WORD PTR [esi+4], 7 ; by adding 2 more to esi. mov esi, arraylong ; Load ESI with the address of the long array. inc DWORD PTR [esi] ; Since a long is 4 bytes long, each inc DWORD PTR [esi+4] ; successive element can be accessed inc DWORD PTR [esi+8] ; by adding 4 more to esi. ret MasmSub ENDP END The following is the output of the program: abc 1 2 3 32768 32769 32770 xyz 8 9 10 32769 32770 32771 Additional query words: mixed language ====================================================================== Keywords : kbLangC kbVC100 kbVC150 kbVC200 kbVC400 kbVC500 kbVC600 Technology : kbVCsearch kbVC400 kbAudDeveloper kbZNotKeyword8 kbvc150 kbvc100 kbCCompSearch kbZNotKeyword3 kbCVC700DOS kbVC500 kbVC600 kbVC200 kbVC32bitSearch kbVC500Search Version : :1.0,1.5,2.0,4.0,5.0,6.0,7.0 Issue type : kbinfo ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. 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