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FML and VIEWS: 16-bit and 32-bit Interfaces
There are two variants of FML. The original FML interface is based on 16-bit values for the length of fields and contains information identifying fields (hence FML16). FML16 is limited to 8191 unique fields, individual field lengths of up to 64K bytes, and a total fielded buffer size of 64K. The definitions, types, and function prototypes for this interface are in fml.h which must be included in an application program using the FML16 interface; and functions live in -lfml.
A second interface, FML32, uses 32-bit values for the field lengths and identifiers. It allows for about 30 million fields, and field and buffer lengths of about 2 billion bytes. The definitions, types, and function prototypes for FML32 are in fml32.h; functions reside in -lfml32. All definitions, types, and function names for FML32 have a "32" suffix (for example, MAXFBLEN32, FBFR32, FLDID32, FLDLEN32, F_OVHD32, Fchg32, and error code Ferror32). Also the environment variables are suffixed with "32" (for example, FLDTBLDIR32, FIELDTBLS32, VIEWFILES32, and VIEWDIR32). For FML32, a fielded buffer pointer is of type "FBFR32 *", a field length has the type FLDLEN32, and the number of occurrences of a field has the type FLDOCC32. The default required alignment for FML32 buffers is 4-byte alignment.
FML16 applications that are written correctly can easily be changed to use the FML32 interface. All variables used in the calls to the FML functions must use the proper typedefs (FLDID, FLDLEN, and FLDOCC). Any call to tpalloc(3c) for an FML typed buffer should use the FMLTYPE definition instead of "FML". The application source code can be changed to use the 32-bit functions simply by changing the include of fml.h to inclusion of fml32.h followed by fml1632.h. The fml1632.h contains macros that convert all of the 16-bit type definitions to 32-bit type definitions, and 16-bit functions and macros to 32-bit functions and macros.
Functions are also provided to convert an FML32 fielded buffer into an FML16 fielded buffer, and vice-versa:
#include "fml.h"
#include "fml32.h"
int
F32to16(FBFR *dest, FBFR32 *src)
int
F16to32(FBFR32 *dest, FBFR *src)
F32to16 converts a 32-bit FML buffer to a 16-bit FML buffer. It does this by converting the buffer on a field-by-field basis and then creating the index for the fielded buffer. A field is converted by generating a FLDID from a FLDID32, and copying the field value (and field length for string and carray fields).
dest and src are pointers to the destination and source fielded buffers, respectively. The source buffer is not changed.
These functions can fail for lack of space; they can be re-issued after enough additional space to complete the operation has been allocated. F16to32 converts a 16-bit FML buffer to a 32-bit FML buffer. It lives in the fml32 library or shared object and sets Ferror32 on error. F32to16 lives in the fml library or shared object and sets Ferror on error. Note that both fml.h and fml32.h must be included to use these functions; fml1632.h may not be included in the same file.
The field types for embedded buffers (FLD_PTR, FLD_FML32 and FLD_VIEW32) are supported only for FML32. Buffers containing FLD_PTR, FLD_FML32, or FLD_VIEW32 fields cause F32to16 to fail with an FBADFLD error. There is no impact when F16to32 is called for these functions.
Note: For the remainder of this section, we describe only the 16-bit functions, without specifying the equivalent FML32 and VIEW32 functions.
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Copyright © 2001 BEA Systems, Inc. All rights reserved.
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