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187 lines
8.7 KiB
Plaintext
187 lines
8.7 KiB
Plaintext
Block Memory Functions
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This library contains functions and variables for accessing data in
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blocks of memory. A block consists of up to 65,535 contiguous bytes.
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This allows for the storage, retrieval, and manipulation of data
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exceeding the maximum array length of 255.
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These functions assume that a block is divided into equally sized segments
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of up to 255 bytes in length. Data in the block is accessed by copying
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data into and out of arrays with the same length as the segment size.
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A segment typically consists of a string field, which is used as a key,
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followed by a number of mixed type fields. For example, the segments in a
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variable table might be 9 bytes long, consisting of a 7 byte variable name
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string (6 characters plus a terminator), the variable type (at index 7)
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and the variable length (at index 8).
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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 <string.h02>
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#include <block.h02>
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The following application variables are defined:
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int blkbgn; Start address of the block.
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int blkend; End address of the block.
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int blklen: Size of Segments in the block.
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These variables must be assigned before calling
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any of the functions in this module. They may be
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reassigned at any time, allowing the program to
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access different blocks.
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Note: Although a block usually begins and ends
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on a 256 byte boundary, this is not required.
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int blkptr; Pointer to the next segment. This can be reset
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to blkbgn using the blkrst() function.
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To preserve the segment position, this value must
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be saved before reassigning to another block, then r
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estored when reassigning back to the original block.
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The following application functions are defined:
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blkset(c); Block Set: Fills entire block with character c,
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leaving block pointer at end of block.
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Should be called with an argument of 0, to initialize
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a block before use.
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blkrst(); Block Reset: Sets block pointer to first segment.
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This routine is called before populating a block with
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calls to the blkput function.
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blknxt(); Block Next: Moves the block pointer to the bext
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segment.
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If the block pointer is moved past the end of the
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block, or the segment length is set to 0, a value of
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#TRUE is returned. Otherwise, a value of #FALSE is
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returned.
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blkprv(); Block Previous: Moves block pointer backward by the
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segment length set by a prior blkseg call.
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If the block pointer is moved past the beginning of
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the block, or the segment length is set to 0, a value
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of #TRUE is returned. Otherwise, a value of #FALSE is
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returned.
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blkput(n ,&m); Block Put: Copies n bytes of array m to a block at the
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current pointer location, and moves block the pointer
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forward by the segment length set by a prior blkseg
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call.
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If the appended bytes would overflow the end of the
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block, no bytes are copied and a value of #FALSE is
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returned. Otherwise, the bytes are copied and a value
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of #TRUE is returned.
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Note: Sets dstlo and dsthi to blklo and blkhi prior
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to the copy, updates blklo and blkhi, then calls
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the memcpy function.
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blkget(n ,&m); Block Get: Copies n bytes from a block at the current
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pointer location to array m, and moves the pointer
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forward by the segment length set by a prior blkseg
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call.
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If the copied bytes would overflow the end of the
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block, no bytes are copied and a value #FALSE is
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returned. Otherwise, the bytes are copied and a value
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of #TRUE is returned.
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Note: Sets dstlo and dsthi to the address of m,
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srclo and srchi to blklo and blkhi prior to the
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copy, updates blkslo and blkshi, then calls the
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memcpy function.
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blkswp(n); Block Swap: Swaps n bytes of array m with the current
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block segment (pointed to by the block pointer. The
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block pointer is not changed.
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Requires a prior call to the memdst function specifying
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an array at least n bytes long, which is used for
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temporary storage.
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Note: Sets temp0 to n, copies blklo and blkhi to dstlo,
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and dsthi, and calls memswp.
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blkmem(n ,&m); Block Memory search: Search block for n byte long
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segment matching array m.
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If a matching segment is found, the value #TRUE is
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returned and the destination pointer is set to the
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address of the matching segment, allowing it to be
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overwritten with a subsequent memcpy call. Otherwise,
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the value #FALSE is returned.
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Note: Sets srclo and srchi to the address of m,
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dstlo and dsthi to the address of the matching segment,
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and temp0 to n. Does not change the block pointer.
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blkstr(n ,&s); Block String Search: Search block for n byte long
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segments beginning with string s.
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If a matching segment is found, the value 255 (true)
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is returned and the segment is copied to the array set
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by a prior memdst call. Otherwise, the value 0 (false)
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is returned.
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Note: Sets srclo and srchi to the address of the
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segment, temp0 to n, and copies dstlo and dsthi to
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temp1 and temp2. Does not change the block pointer.
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blksrt(&m); Block Sort: Sort segments in block by initial string,
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using array m as temporary storage.
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Segments are sorted in alphabetical order, with segment
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length set by a prior blkseg call, and sorting stops at
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the first segment that begins with an empty string (the
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first byte is 0), leaving the block pointer at that
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segment.
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Note: Uses the selection sort algorithm. Sets temp1
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and temp2 to the address of array m.
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blkdst(); Block Destination: Sets the destination pointer to the
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block segment pointer.
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This is a utility function called by other functions in
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this module.
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Note: Sets dstlo and dsthi to blklo and blkhi.
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Note: This library expects the following functions to be defined
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setdst(&s); Set destination string pointer
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setsrc(&s); Set source string pointer and initialize index
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memcmp Compare memory
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memcpy Copy memory
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memsrc Set memory source and count
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strcml Compare string (alternate entry point)
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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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blklo, blkhi Block Pointer
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the static variable
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blkslo, blkshi Block Start Address
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blkelo, blkehi Block End Address
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blklen Block Segment Length
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as well as the transient variables
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temp0, temp1, temp2 Temporary storage
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