Encyclopedia of Graphics File Formats Companion

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Text File | 1994-04-28 | 36.6 KB | 884 lines

PROGRAMMERS MANUAL FOR IMAGE DISPLAY AND I/O ROUTINES IMDISP is written in a modular way so that it is easy to change it to work with different display devices or on other computers. The code can also easily be adapted for use in other application programs. There are device dependent image display modules, general image display subroutines, image I/O routines, and image label and command line parsing routines. The general purpose display routines can draw lines, write text with different fonts, manipulate a cursor, interactively adjust the palette, display histograms, etc. The IMDISP system is written in the "C" computer langauge. Model of Device Independent Image Display The image display is modeled as having coordinates ranging from 1 to "dispnl" from top to bottom and from 1 to "dispns" from left to right (i.e. a line-sample space). There is one image plane that can take on "numDN" values. There is assumed to be a lookup table to convert those DN values into voltages for the red, green, and blue guns in the monitor. There are "numshades" shades of each primary color for a total of numshades**3 different colors. The palette is a table of numDN entries, with each entry containing the three primary color intensities on a scale from 0 to 255. There are five global variables that define the display characteristics and are set in the DISPDRIV module: dispnl, dispns, numDN, numshades, OneScreen. There are two related contants: MAXDISPNL and MAXDISPNS. The cursor, text, and font global variables are in the DISPUTIL module. The image control block constants and variables are in the IMAGEIO module. Compiling and Linking Routines This document describes the "C" language version of the IMDISP system. The routines are written in Microsoft C version 5.1 on an IBM AT compatible computer. The large memory module is used. There is one module (dispsub.asm) written in 8086 assembly language for reasons of execution speed. The following commands are are used to compile and link the subroutines and programs. They are contained in the COMPLINK.BAT file. cl /AL /c dispio.c disputil.c fileio.c fileutil.c imageio.c imagutil.c imdisp.c labutil.c memutil.c masm dispsub.asm; link/NOE imdisp+dispsub+dispio+disputil+fileio+filesel+imagutil+ imageio+labutil+memutil/stack:8000/exepack; LIST OF PROGRAMS IMDISP.C - Main program, help, command drivers. DISPIO.C - Display on/off, read/write lines, pixels, palette. DISPUTIL.C - Font, cursor, text and palette routines. DISPSUB.ASM - Assembly language routines for EGA/PGA display. FILEIO.C - MSDOS and CDROM file input/output routines. FILEUTIL.C - File menu and wild card routines. IMAGEIO.C - Image open/close/read routines. IMAGUTIL.C - Palette, histogram, profile and stretch routines. LABUTIL.C - Label parsing routines. MEMUTIL.C - Special memory allocation routines (malloc/free). ----------------------------------------------------------------- Routines for image display Device dependant routines: Module: DISPIO DisplayOn DisplayOff WritePalette (palette) WritePixel (line, sample, DNvalue) ReadPixel (line, sample, DNvalue) DisplayLine (buffer, line, samp, ns) ClearDisplay (DNvalue) PutRefresh (buffer, line, ss, ns) GetRefresh (buffer, line, ss, ns) Device independant routines: Module: DISPUTIL InitDisplay ReadPalette (palette) DrawLine (line1, sample1, line2, sample2, DNvalue) DrawBox (line, samp, linesize, sampsize, DNvalue) RemoveCursor PlaceCursor (line, sample, DNvalue) MoveCursor (line, sample) Font (FontType) DrawText (text, line, sample, height, angle, DNvalue) LengthText (text, height, TextLength) TypeText (text) TypeTextLine (text) AcceptText (string) WriteText (text) Module: FILEUTIL int FileSel(selFilename) int Wildexp(argc, argv) Module: IMAGUTIL DiddlePalette (numcolors) DisplayHistogram (histbuffer, numbins, minDN, maxDN) Stretch (DNlow, DNhigh : Integer); Profile Routines for image I/O Module: IMAGEIO OpenImage (filename, unit, IOmode, nl, ns, bitsperpix, status) ReadLine (unit, buffer, line, ss, ns, status) WriteLine (unit, buffer, line, ss, ns, status) CloseImage (unit, status) CheckStatus (status) ConvertLine (inbuffer, outbuffer, inbits, outbits, ns, status) Module: LABUTIL GetLabelInteger (LabelBuf, Len, Keyword, default, value, flag) GetLabelReal (LabelBuf, Len, Keyword, default, value, flag) GetLabelString (LabelBuf, Len, Keyword, default, value, flag) InterpretLabel (LabelBuf, Len, labelsize, nline, nsamp, bitsperpix, reclen, lineheadbytes, DetachedFilename) MakeLabel (LabelBuf, labelsize, nline, nsamp, bitsperpix, reclen) Function GetCommand (CommandString, CommandList) GetKeywordInteger (CommandString, Keyword, default, value, flag) GetKeywordReal (CommandString, Keyword, default, value, flag) GetKeywordString (CommandString, Keyword, default, value, flag) Block I/O routines Module: FILEIO OpenFile (filename, unit, IOmode, blocksize, status) ReadBlocks (unit, buffer, StartBlock, NumBlocks, BlocksRead, status) WriteBlocks (unit, buffer, StartBlock, NumBlocks, status) CloseFile (unit, status) InitializeCD (status) ReadBlocksCD (buffer, StartBlock, NumBlocks, status) SUMMARY AND USE OF SUBROUTINES /*** Module: DISPIO DISPIO contains the device dependent display routines for the Color Graphics Adapter (CGA), the Enhanced Graphics Adapter (EGA), the Professional Graphics Adapter (PGA), and the Video Graphics Array (VGA). The global variables that define the device are allocated and initialized here. ***/ DisplayOn() /*** DisplayOn figures out which display device is on the system and then initializes for that device. The device is turned on. The global variables that define the display characteristics and the default color palette are initialized. The refresh buffer is zeroed. ***/ DisplayOff() /*** DisplayOff turns off the display device returning the screen to text mode. ***/ WritePalette (coltab) /*** WritePalette updates the display device palette with the palette passed in coltab. coltab must be of type Color. ***/ WritePixel (line, sample, DN) /*** WritePixel writes a pixel on the display screen. Parameter type description line integer The line coordinate of the pixel sample integer The sample coordinate of the pixel DN integer The DN value of the pixel ***/ ReadPixel (line, sample, p_DN) /*** ReadPixel read a pixel value from the display screen. Parameter type description line integer The line coordinate of the pixel sample integer The sample coordinate of the pixel p_DN int ptr The DN value of the pixel is returned ***/ DisplayLine (buffer, line, sample, ns) /*** DisplayLine writes a line of pixels on the display screen. Parameter type description buffer char ptr The array of pixel values line integer The line coordinate of the first pixel sample integer The sample coordinate of the first pixel ns integer The number of pixels to display ***/ ClearDisplay (DN) /*** ClearDisplay sets the whole display to a particular value. Parameter type description DN integer The DN value to set (usually 0) ***/ PutRefresh (buffer, line, ss, ns) /*** PutRefresh stores a line of pixels in the refresh buffer. Parameter type description buffer char ptr The array of pixel values line integer The line coordinate of the first pixel sample integer The sample coordinate of the first pixel ns integer The number of pixels to store ***/ GetRefresh (buffer, line, ss, ns) /*** GetRefresh reads a line of pixels from the refresh buffer. Parameter type description buffer char ptr The receiving array of pixel values line integer The line coordinate of the first pixel sample integer The sample coordinate of the first pixel ns integer The number of pixels to read ***/ -------------------------------------------------------------------------- /*** Module: DISPUTIL Device Independant General Purpose Graphics Routines Includes line drawing, text display, and cursor routines. ***/ InitDisplay() /*** InitDisplay turns the display device on, loads the default palette, initializes the global variables, and loads the font arrays. ***/ ReadPalette (coltab) /*** ReadPalette returns the current color palette in coltab. coltab is of type Color. ***/ DrawLine (x1, y1, x2, y2, color) /*** DrawLine draws a line of pixels from the first point to the second point with the desired DN value. Clipping is not performed. Parameter Type Description x1 int the line coordinate of the first point y1 int the sample coordinate of the first point x2 int the line coordinate of the second point y2 int the sample coordinate of the second point color int the DN value of the drawn pixels ***/ DrawBox (line, samp, lsize, ssize, color) /*** DrawBox draws a solid rectangle on the screen. Used for erasing parts of the screen. Parameter Type Description line int starting line coordinate of rectangle samp int starting sample coordinate of rectangle lsize int number of lines in rectangle ssize int number of samples in rectangle color int the DN value to draw the box ***/ Font (FontType) /*** Font reads in the font file for type FontType and fills the font arrays appropriately. If FontType = 0 the internal font file is used instead. FontType = 5 reads in font file 005.FNT, etc. The global variable thefont is set to the font number. The format of a font file is a sequence of bytes. The first byte is the number of characters defined in the font. For each character there is the following: the ascii code, the number of line strokes, the character width, and then the list of line strokes. Each line stroke consists of three bytes: the pen motion, and the x and y coordinate. The width, x, and y values are converted back into character coordinates by subtracting 50 and dividing by 100. The pen is 2 for pen down, and 3 for pen up. ***/ DrawText (text, line, sample, height, angle, DNvalue) /*** DrawText draws a text string on the display using the current font. Parameter Type Description text char ptr text string to display line int line coordinate of lower left of first char sample int sample coordinate of lower left of first char height int height of characters in pixels angle int angle in degrees ccw from positive sample direction DNvalue int the DN value to draw the pixels in with ***/ LengthText (text, height, p_TextLength) /*** LengthText finds the length in pixels of a given text string. Parameter Type Description text char ptr text string to display height int height of characters in pixels p_TextLength int ptr where to return length of string ***/ TypeText (TypeString) /*** TypeText displays a line of text on the screen at the current text location with a height of 15 pixels. The area is first erased. The text position is advanced to the next position after the last character. Parameter Type Description TypeString char ptr text string to display ***/ TypeTextLine (TypeString) /*** TypeTextLine displays a line of text on the screen using TypeText. The text position is advanced to the beginning of the next line. Parameter Type Description TypeString char ptr text string to display ***/ AcceptText (AcceptString) /*** AcceptString gets a string from the keyboard. The characters are echoed on the display screen using DrawText. The string is terminated with a return (ascii 13). Backspace deleting is supported. The text position is left at the beginning of the next line. Parameter Type Description AcceptString char ptr returned text string from user ***/ WriteText (text) /*** WriteText writes out a line of text to the user. If there is only one screen then the text is written on the image display. Otherwise it is written to the terminal. Parameter Type Description text char ptr text string to display ***/ RemoveCursor() /*** RemoveCursor removes the cursor, if it is on, from the display screen, replacing the original pixel values. ***/ PlaceCursor (line, sample, cursDN) /*** PlaceCursor puts the cursor, if it is not already on, on the screen, while storing the original pixel values. Parameter Type Description line int the line coordinate to put the cursor at sample int the sample coordinate to put the cursor at cursDN int the DN value of the cursor ***/ MoveCursor (p_line, p_sample) /*** MoveCursor performs the cursor mode operation. The user moves the cursor around using the numeric keypad. The cursor moves in discrete steps whose size can be changed. The final cursor position is returned. Parameter Type Description p_line int ptr the cursor line coordinate p_sample int ptr the cursor sample coordinate ***/ -------------------------------------------------------------------------- /*** Module: IMAGUTIL Special Purpose Device Independant Display Routines Contains high level display routines such as interactive palette adjustment, histogram display, and image profile drawing. ***/ DiddlePalette (numdiddle) /*** DiddlePalette performs interactive adjustment of the color palette. A wedge of numdiddle DN values, from 0 to the maximum, is displayed at the bottom of the screen, and the palette is changed to have only numdiddle distinct shades. Then a loop for user input is entered. The active color is the one in the wedge with the small black box inside it. The following is a list of commands: Character Action 4 (6) move to next lower (higher) color in wedge r (R) decrease (increase) amount of red one notch g (G) decrease (increase) amount of green one notch b (B) decrease (increase) amount of blue one notch 2 (8) decrease (increase) amount of all colors one notch . exit from palette diddle mode The wedge is erased after the user exits. Parameter Type Description numdiddle int number of colors in the wedge and resulting palette ***/ DisplayHistogram (histbuf, numbins, minDN, maxDN) /*** DisplayHistogram diplays the passed histogram on the screen. The third highest bin in the histogram is used to scale the plot. The axes of the plot are labeled and annotated. The number in each bin is indicated by the length of the line drawn vertically from the axis. Parameter Type Description histbuf long int array the array of count values for each bin numbins int the number of bins in the histogram minDN int the minimum DN value in the histogram maxDN int the maximum DN value in the histogram ***/ Stretch (DNlow, DNhigh) /*** Stretch applies a linear gray scale ramp to the palette starting with 0 at Dnlow and proceeding to 255 at DNhigh. Parameter Type Description DNlow int the starting DN value of the linear ramp DNhigh int the ending DN value of the linear ramp ***/ Profile() /*** Profile plots a profile of the pixel values between two points on the screen. Cursor mode is used to select the two endpoints. A line is drawn between the endpoints and a plot of DN value versus distance along the line is made. ***/ -------------------------------------------------------------------------- /*** Module: IMAGEIO Image I/O routines for labeled images Includes routines for opening images, reading and writing image lines, and converting pixel formats. ***/ OpenImage (filename, unit, IOmode, p_nline, p_nsamp, p_bitsperpix, status) /*** OpenImage opens an image file either for reading or writing. The size of the image and pixel format are returned if the file is opened for reading. If the file is opened for writing then the passed number of lines and samples and pixel format are used for the new image. The unit number is used to refer to the file in subsequent operations. If the file is opened for input then the label processing routines will parse Vicar2 and PDS labels and will prompt for user info if the image is unlabeled. PDS detached labels are handled transparently in this routine. If the file is for writing then a PDS label will be output. An error is returned if there is insufficient room to dynamically allocate the image buffer, or if there is a file error. For images with pixel sizes less than a byte, each line is assumed to start with a new byte. Parameter Type In/out Description filename char ptr in Name of image file to open unit int in Unit number of image (0,1,2...) IOmode char ptr in Access mode of file ("r..." for reading, "w..." for writing) p_nline int ptr in/out The number of lines in the image p_nsamp int ptr in/out The number of samples in the image p_bitsperpix int ptr in/out The number of bits in a pixel (pixel format) (16 for integer, 8 for byte, 4 for nibble, 1 for binary) status char ptr out Return string with error message (0 length string if no error) ***/ ReadLine (unit, buffer, line, ss, ns, status) /*** ReadLine reads a line of pixels from the image into the user's buffer. The reading is completely random access, the lines may be read in any order; it is more efficient, however, to read lines sequentially. Partial image lines may be read. The output data is in the same format as the file (the convert routine may be used to convert pixel formats). Parameter Type In/out Description unit int in Unit number of image (same as in open) buffer char ptr out Buffer to receive pixels line int in The number of the image line to read (1 is first) ss int in The starting sample in the line ns int in The number of samples to read into buffer status char ptr out Return string with error message (0 length string if no error) ***/ WriteLine (unit, buffer, line, ss, ns, status) /*** WriteLine writes a line of pixels from the user buffer to the image. Although the writing is buffered, completely random access will not work; the image lines should be written sequentially. Partial image lines may be written. The input data must be in the same format as the file (no conversion is performed). Parameter Type In/out Description unit int in Unit number of image (same as in open) buffer char ptr in Buffer of image pixels line int in The number of the image line to write ss int in The starting sample in the line ns int in The number of samples to write from buffer status char ptr out Return string with error message (0 length string if no error) ***/ CloseImage (unit, status) /*** CloseImage closes the image file. If the image is opened for writing then the image buffer is first flushed. Parameter Type In/out Description unit int in Unit number of image (same as in open) status char ptr out Return string with error message (0 length string if no error) ***/ CheckStatus (status) /*** CheckStatus checks the status string passed in. If there is no error the routine returns, otherwise the error message is printed to the terminal and the program is aborted. ***/ ConvertLine (inbuffer, outbuffer, inbits, outbits, ns, status) /*** ConvertLine converts a line of pixels into a different format. Parameter Type In/out Description inbuffer char ptr in The input buffer of pixels outbuffer char ptr out The output buffer of pixels inbits int in The pixel format of the input buffer outbits int in The pixel format of the output buffer ns int in The number of samples to convert status char ptr out Return string with error message Conversions supported : outbits 1 4 8 16 inbits 1 . - . . . means supported 4 - . . . 8 . . . . 16 . . . . ***/ -------------------------------------------------------------------------- /*** Module: LABUTIL Label Processing Routines ***/ GetLabelInteger (LabelBuf, LabelBufLen, Keyword, defaul, p_value, p_flag) /*** GetLabelInteger returns the integer value following the keyword in the label buffer. If the keyword is not there then the default value is returned. The flag indicates whether the keyword is there. Parameter Type In/out Description LabelBuf char ptr in The buffer containing the label LabelBufLen int in The length in bytes of the label buffer Keyword char ptr in The keyword string to match defaul int in The value to return if no keyword or value p_value int ptr out The returned value p_flag int ptr out The flag: -1 if no keyword match 0 if illegal value, 1 if keyword and value ***/ GetLabelReal (LabelBuf, LabelBufLen, Keyword, defaul, p_value, p_flag) /*** GetLabelReal returns the real value following the keyword in the label buffer. If the keyword is not there then the default value is returned. The flag indicates whether the keyword is there. Parameter Type In/out Description LabelBuf char ptr in The buffer containing the label LabelBufLen int in The length in bytes of the label buffer Keyword char ptr in The keyword string to match defaul float in The value to return if no keyword or value p_value float ptr out The returned value p_flag int ptr out The flag: -1 if no keyword match 0 if illegal value, 1 if keyword and value ***/ GetLabelString (LabelBuf, LabelBufLen, Keyword, defaul, value, p_flag) /*** GetLabelString returns the string value following the keyword in the label buffer. If the keyword is not there then the default value is returned. The flag indicates whether the keyword is there. Parameter Type In/out Description LabelBuf char ptr in The buffer containing the label LabelBufLen int in The length in bytes of the label buffer Keyword char ptr in The keyword string to match defaul char ptr in The value to return if no keyword or value p_value char ptr out The returned value p_flag int ptr out The flag: -1 if no keyword match 0 if illegal value, 1 if keyword and value ***/ InterpretLabel (buf, len, p_labelsize, p_nline, p_nsamp, p_bitsperpix, p_reclen, p_lineheadbytes, DetachedFileName) /*** InterpretLabel interprets the label in the buffer to extract the image information. First something is identified to determine whether the image has a PDS label or a Vicar2 label or no label. If the image is labeled then the appropriate keyword values are extracted, otherwise the user is prompted for the into. Parameter Type In/out Description buf char ptr in The label buffer len int in The length in bytes of the label buffer p_labelsize int ptr out The size of the label or header to skip p_nline int ptr out The number of lines in the image p_nsamp int ptr out The number of samples in the image p_bitsperpix int ptr out The pixel format (16,8,4,1) p_reclen int ptr out The record length in bytes p_lineheadbytes int ptr out The header bytes at beginning of each line DetachedFileName char ptr out The name of the file of data null string if no detached label ***/ MakeLabel (Buf, p_labelsize, nline, nsamp, bitsperpix, reclen) /*** MakeLabel creates a PDS label in the buffer, having the appropriate image parameters. Parameter Type In/out Description Buf char ptr out The label buffer p_labelsize int ptr out The size of the label nline int out The number of lines in the image nsamp int out The number of samples in the image bitsperpix int out The pixel format (16,8,4,1) reclen int out The record length in bytes ***/ int GetCommand (CommandString, CommandList) /*** GetCommand is an integer function that returns the number of the command that is in the beginning of the CommandString parameter. The command is assigned a number according to the list of commands in the CommandList string parameter. The list of commands should be in uppercase and have spaces between the commmand. ***/ GetKeywordInteger (CommandString, Keyword, defaul, p_value, p_flag) /*** GetKeywordInteger scans the CommandString for the Keyword and returns the value of the following integer. Parameter Type In/out Description CommandString char ptr in The command string to scan thru Keyword char ptr in The keyword string to match defaul int in The default value to return if no keyword or illegal value p_value int ptr out The returned value p_flag int ptr out The flag: -1 for no keyword match 0 for keyword with no/bad value 1 for keyword and good value ***/ GetKeywordReal (CommandString, Keyword, defaul, p_value, p_flag) /*** GetKeywordReal scans the CommandString for the Keyword and returns the value of the following real. Parameter Type In/out Description CommandString char ptr in The command string to scan thru Keyword char ptr in The keyword string to match defaul float in The default value to return if no keyword or illegal value p_value float ptr out The returned value p_flag int ptr out The flag: -1 for no keyword match 0 for keyword with no/bad value 1 for keyword and good value ***/ GetKeywordString (CommandString, Keyword, defaul, value, p_flag) /*** GetKeywordString scans the CommandString for the Keyword and returns the value of the following string. Parameter Type In/out Description CommandString char ptr in The command string to scan thru Keyword char ptr in The keyword string to match defaul char ptr in The default value to return if no keyword or illegal value p_value char ptr out The returned value p_flag int ptr out The flag: -1 for no keyword match 0 for keyword with no/bad value 1 for keyword and good value ***/ -------------------------------------------------------------------------- /*** Module: FILEIO Contains block level I/O routines for MS-DOS files. ***/ OpenFile (filename, unit, IOmode, p_blocksize, status) /*** OpenFile opens a file with the given file name. The file may be open for reading or writing. If the file name begins with "CD:" then it is assumed to be an absolute CD-ROM file on a non-standard CD-ROM. The file name is of the form "CD:mm:ss:bb", where mm is the minute of the starting sector, ss is the second, and bb is the block number within the second. The logical blocksize to be used in the image I/O routines is returned. Parameter Type In/out Description filename char ptr in File name string unit int in Unit number (0,1,2...) IOmode char ptr in "r..." for reading, 'w...' for writing p_blocksize int ptr out The returned logical blocksize to use status char ptr out The error message string (0 length for no error) ***/ ReadBlocks (unit, buffer, startblock, numblocks, p_blocksread, status) /*** ReadBlocks reads blocks from the file into the buffer. Parameter Type In/out Description unit int in Unit number from open buffer char ptr out The output buffer of data startblock long int in The starting logical block numblocks int in The number of blocks to read p_blocksread int ptr out The number of blocks actually read status char ptr out The error message string (0 length for no error) ***/ WriteBlocks (unit, buffer, startblock, numblocks, status) /*** WriteBlocks writes blocks from the buffer to the file. Parameter Type In/out Description unit int in Unit number from open buffer char ptr in The input buffer of data startblock long int in The starting logical block numblocks int in The number of blocks to write status char ptr out The error message string (0 length for no error) ***/ CloseFile (unit, status) /*** CloseFile closes the file. Parameter Type In/out Description unit int in Unit number from open status char ptr out The error message string (0 length for no error) ***/ -------------------------------------------------------------------------- InitializeCD (p_PB_size, status) /*** InitializeCD initializes the CD player and returns the physical block size. Parameter Type Description p_PB_size int ptr The size of the physical blocks for this driver. (in this case 2048 bytes) status char ptr Error message string (0 length if no error) ***/ ReadBlocksCD (buffer, StartPB, NumPB, status) /*** ReadBlocksCD reads blocks from the CD-ROM to the user's buffer. Parameter Type Description buffer char ptr Buffer to receive data StartPB long int The starting absolute physical block NumPB int The number of physical blocks to read status char ptr Error message string (0 length if no error) ***/ -------------------------------------------------------------------------- Low Level Block I/O with MS-DOS for non-standard CD-ROM's InitializeCD (p_PB_size, status) /*** InitializeCD initializes the CD player and returns the physical block size. Parameter Type Description p_PB_size int ptr The size of the physical blocks for this driver. (in this case 2048 bytes) status char ptr Error message string (0 length if no error) ***/ ReadBlocksCD (buffer, StartPB, NumPB, status) /*** ReadBlocksCD reads blocks from the CD-ROM to the user's buffer. Parameter Type Description buffer char ptr Buffer to receive data StartPB long int The starting absolute physical block NumPB int The number of physical blocks to read status char ptr Error message string (0 length if no error) ***/ -------------------------------------------------------------------- /*** Module: FILEUTIL Contains file selection and wildcard expansion routines. ***/ int FileSel(selFilename) /*** filesel -- allow user to browse directories and select image files for display. Returns selected file name. Parameter Type Description selFilename char ptr filename selected for processing. ***/ wildexp(oargcp, oargvp) /*** wildexp -- expand wildcard file name. Returns array of pointers to filenames meeting wildcard specifications. Parameter Type Description oargcp int ptr pointer to number of values in oargvp oargvp char ptr ptr ptr pointers to text strings containing file names meeting wild card specification. ***/ Memory Allocation Procedures Willard Gersbacher - CompuServe User ID: (76117,2611) The procedures included in this archive provide functionally equivalent memory allocation procedures for the main memory procedures used in C. These procedures were written primarily because of a need to minimize memory usage for a large program under development. The MSC 5.1 library procedures were not satisfactory for this application because they did not release memory back to the system when it was 'free'ed. Additionally, they tended to allocate too much memory under certain circumstances which lead to a reduction in space available for other programs and data which were currently active at the time. These procedures should only be used with large data model programs (i.e., compact, large, and huge memory models). No provision has been made for small or medium model programs. /* The following routines from the ALLOC.ARC distribution file have all been incorporated in MEMUTIL.C */ free.c - Functional equivalent to free. Included in this file is an additional procedure _ffree which calls free. malloc.c - Functional equivalent of malloc. This file also contains the memory structures which are used to keep track of the blocks of memory allocated. In addition, the procedure _fmalloc is defined which just makes a call to malloc. memutil.c - This file contains a set of procedures which are used by the main memory allocation procedures to maintain the memory structure used to keep track of the user allocations and frees. reduceal.c - This procedure may be called to reduce the memory allocated to a program. It attempts to release back to DOS the memory not currently being used. reducedd.c - This procedure may be called to reduce the default data segment to the minimum size required. Normally this should be called before any calls to memory allocation procedures. Included in this file are dummy procedures for _nmalloc and _nfree. These latter procedures were included because some of the MSC library uses the near heap for memory allocation (even though you may be using large data model programs). Since this procedure does away with any space which might be used for near heap allocation, this forces the procedures which call them to use the 'far' heap.