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143 lines
5.8 KiB
Plaintext
143 lines
5.8 KiB
Plaintext
Sta Functions
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This module contains functions to access and manipulate a stack structure.
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The entries on a stack are stored in contiguous bytes of memory.
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Each element of the stack can vary in size from 1 to 255 bytes. Both
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arrays and strings may be pushed onto and pulled off the stack.
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Usage: at the beginning of the program use the directives
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#include <stddef.h02>
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#include <memory.h02>
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#include <stack.h02>
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The following application functions are defined:
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stkbgn(&b); Stack Begin: Sets the beginning of the stack
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to address b.
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The beginning of a stack is the first byte
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of memory in the stack space.
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Although stack space usually begins on a 256
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byte boundary, this is not required.
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Note: Sets variables stkslo and stkshi.
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stkend(&e); Stack End: Sets the end of the stack to address
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e. The end of a stack is the byte after the last
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byte of memory in the stack space.
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Although stack space usually ends on a 256
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byte boundary, this is not required.
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Note: Sets variables stkelo and steshi.
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stkrst(); Stack Reset: Set stack pointer to stack begin
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address.
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This routine is called before populating a
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stack with calls to the stkpsh function.
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r = stkpsh(n ,&m); Stack Push: Creates a new entry at the end of
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the stack consisting of n bytes of array m.
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If n is 0 or the new entry would overflow the
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end of the stack space, no entry is created and
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a value of 0 is returned. Otherwise, the number
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of bytes in the new entry is returned.
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Note: Sets dstlo and dsthi to stkslo and stkhi
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prior to the copy, updates stkslo and stkshi,
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then calls the memcpy function.
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r = stkpop(&m); Stack Pop: Copies the bytes from the last entry of
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the stack into array m and removes the entry from
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the stack.
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If the stack is empty, the value 0 is returned.
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Otherwise, the number of bytes in the popped entry
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is returned.
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Note: Sets dstlo and dsthi to the address of m,
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updates stklo and stkhi to point to the beginning
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of the last entry, sets srclo and srchi to stklo
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and stkhi, then calls the memcpy function.
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r,m,l = stksiz(); Stack Size: Calculates and returns the current size
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of the stack along with a flag indicating whether
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the stack is populated or empty.
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The first byte returned will be 255 (True) if the
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stack contains at least one entry, or 0 (False) if
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the stack is empty. The second and third returned
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bytes are the size of the stack as a sixteen bit
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number, most-significant and least-significant byte,
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respectively.
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Note: Subtracts the sixteen bit value contained in
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stkslo and stkhi from the value in stklo and stkhi.
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The following utility functions are not normally used in applications:
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*,m,l = stkptr(); Stack Pointer: Returns the address contained in
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the stack pointer as the most significant byte
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and the least significant byte.
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Note: Reads variables stklo and stkhi.
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stkset(&d); Stack Set: Sets stack pointer to address d.
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Note: Sets variables stklo and stshi.
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stkadd(b); Stack Add: Increases the stack pointer by b.
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Note: Updates variables stklo and stshi.
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stksub(b); Stack Subtract: Decreases the stack pointer by b.
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Note: Updates variables stslo and stshi.
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stkinc(b); Stack Increment: Increases the stack pointer by 1.
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Note: Updates variables stklo and stshi.
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stkdec(b); Stack Decrement: Secreases the stack pointer by 1.
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Note: Updates variables stslo and stshi.
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stkssp(); Save Stack Pointer: Copies contents of the stack
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pointer to variables temp1 and temp2.
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Note: Calls stkptr() then savrxy().
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stkrsp(); Restore Stack Pointer: Copies contents of variables
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temp1 and temp2 to the stack pointer.
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Note: Calls resrxy() then stkset().
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Note: This module expects the following functions to be defined
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memcpl Copy memory (alternate entry point)
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ressrc Restore source pointer
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resrxy Restore X and Y registers
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savrxy Save X and Y registers
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setdst Set destination pointer
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setsrc Set source pointer and initialize index
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along with the zero page variable pairs
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srclo, srchi Source String Pointer
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dstlo, dsthi Destination String Pointer
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stklo, stkhi stack Pointer
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the static variables
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stkslo, stkshi Stack Start Address
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stkelo, stkehi Stack End Address
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and the transient variables
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temp0, temp1, temp2 Temporary storage
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