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284 lines
7.3 KiB
NASM
284 lines
7.3 KiB
NASM
; Manages both constants and labels within a same namespace and registry.
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;
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; Local Labels
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;
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; Local labels during the "official" first pass are ignored. To register them
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; in the global registry during that pass would be wasteful in terms of memory.
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;
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; What we don instead is set up a separate register for them and have a "second
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; first pass" whenever we encounter a new context. That is, we wipe the local
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; registry, parse the code until the next global symbol (or EOF), then rewind
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; and continue second pass as usual.
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; *** Constants ***
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; Maximum number of symbols we can have in the global registry
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.equ SYM_MAXCOUNT 0x200
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; Maximum number of symbols we can have in the local registry
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.equ SYM_LOC_MAXCOUNT 0x40
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; Size of the symbol name buffer size. This is a pool. There is no maximum name
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; length for a single symbol, just a maximum size for the whole pool.
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.equ SYM_BUFSIZE 0x2000
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; Size of the names buffer for the local context registry
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.equ SYM_LOC_BUFSIZE 0x200
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; *** Variables ***
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; Each symbol is mapped to a word value saved here.
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.equ SYM_VALUES SYM_RAMSTART
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; A list of symbol names separated by null characters. When we encounter a
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; symbol name and want to get its value, we search the name here, retrieve the
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; index of the name, then go get the value at that index in SYM_VALUES.
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.equ SYM_NAMES SYM_VALUES+SYM_MAXCOUNT*2
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; Registry for local labels. Wiped out after each context change.
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.equ SYM_LOC_VALUES SYM_NAMES+SYM_BUFSIZE
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.equ SYM_LOC_NAMES SYM_LOC_VALUES+SYM_LOC_MAXCOUNT*2
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; Pointer to the currently selected registry
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.equ SYM_CTX_NAMES SYM_LOC_NAMES+SYM_LOC_BUFSIZE
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.equ SYM_CTX_NAMESEND SYM_CTX_NAMES+2
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.equ SYM_CTX_VALUES SYM_CTX_NAMESEND+2
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; Pointer, in (SYM_CTX_VALUES), to the result of the last symFind
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.equ SYM_CTX_PTR SYM_CTX_VALUES+2
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.equ SYM_RAMEND SYM_CTX_PTR+2
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; *** Code ***
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; Advance HL to the beginning of the next symbol name in SYM_NAMES except if
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; (HL) is already zero, meaning we're at the end of the chain. In this case,
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; do nothing.
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; Sets Z if it succeeded, unset it if there is no next.
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_symNext:
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xor a
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cp (hl)
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jr nz, .do ; (HL) is not zero? we can advance.
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; (HL) is zero? we're at the end of the chain.
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call unsetZ
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ret
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.do:
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; A is already 0
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call findchar ; find next null char
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; go to the char after it.
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inc hl
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cp a ; ensure Z
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ret
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symInit:
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xor a
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ld (SYM_NAMES), a
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ld (SYM_LOC_NAMES), a
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; Continue to symSelectGlobalRegistry
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symSelectGlobalRegistry:
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push af
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push hl
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ld hl, SYM_NAMES
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ld (SYM_CTX_NAMES), hl
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ld hl, SYM_NAMES+SYM_BUFSIZE
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ld (SYM_CTX_NAMESEND), hl
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ld hl, SYM_VALUES
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ld (SYM_CTX_VALUES), hl
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pop hl
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pop af
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ret
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symSelectLocalRegistry:
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push af
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push hl
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ld hl, SYM_LOC_NAMES
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ld (SYM_CTX_NAMES), hl
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ld hl, SYM_LOC_NAMES+SYM_LOC_BUFSIZE
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ld (SYM_CTX_NAMESEND), hl
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ld hl, SYM_LOC_VALUES
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ld (SYM_CTX_VALUES), hl
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ld a, h
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ld a, l
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pop hl
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pop af
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ret
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; Sets Z according to whether label in (HL) is local (starts with a dot)
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symIsLabelLocal:
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ld a, '.'
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cp (hl)
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ret
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; Place HL at the end of (SYM_CTX_NAMES) end (that is, at the point where we
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; have two consecutive null chars and DE at the corresponding position in
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; SYM_CTX_VALUES).
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; If we're within bounds, Z is set, otherwise unset.
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symNamesEnd:
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push ix
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push bc
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ld ix, (SYM_CTX_VALUES)
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ld hl, (SYM_CTX_NAMES)
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ld de, (SYM_CTX_NAMESEND)
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.loop:
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call _symNext
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jr nz, .success ; We've reached the end of the chain.
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inc ix
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inc ix
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; Are we out of bounds name-wise?
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call cpHLDE
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jr nc, .outOfBounds ; HL >= DE
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; are we out of bounds value-wise? check if IX == (SYM_CTX_NAMES)
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; Is is assumed that values are placed right before names
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push hl
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push ix \ pop bc
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ld hl, (SYM_CTX_NAMES)
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sbc hl, bc
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pop hl
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jr z, .outOfBounds ; IX == (SYM_CTX_NAMES)
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jr .loop
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.outOfBounds:
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call unsetZ
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jr .end
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.success:
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push ix \ pop de ; our values pos goes in DE
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cp a ; ensure Z
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.end:
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pop bc
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pop ix
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ret
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; Register label in (HL) (minus the ending ":") into the symbol registry and
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; set its value in that registry to DE.
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; If successful, Z is set and A is the symbol index. Otherwise, Z is unset and
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; A is an error code (ERR_*).
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symRegister:
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call symFind
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jr z, .alreadyThere
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push hl ; will be used during processing. it's the symbol to add
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push de ; will be used during processing. it's our value.
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; First, let's get our strlen
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call strlen
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ld c, a ; save that strlen for later
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call symNamesEnd
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jr nz, .outOfMemory
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; Is our new name going to make us go out of bounds?
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push hl
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push de
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ld de, (SYM_CTX_NAMESEND)
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ld a, c
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call addHL
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call cpHLDE
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pop de
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pop hl
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jr nc, .outOfMemory ; HL >= DE
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; Success. At this point, we have:
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; HL -> where we want to add the string
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; DE -> where the value goes
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; SP -> value to register
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; SP+2 -> string to register
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; Let's start with the value.
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push hl \ pop ix ; save HL for later
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pop hl ; value to register
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call writeHLinDE ; write value where it goes.
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; Good! now, the string.
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pop hl ; string to register
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push ix \ pop de ; string destination
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; Copy HL into DE until we reach null char
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call strcpyM
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; We need to add a second null char to indicate the end of the name
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; list. DE is already correctly placed, A is already zero
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ld (de), a
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cp a ; ensure Z
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; Nothing to pop. We've already popped our stack in the lines above.
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ret
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.outOfMemory:
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ld a, ERR_OOM
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call unsetZ
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pop de
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pop hl
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ret
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.alreadyThere:
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; We are in a tricky situation with regards to our handling of the
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; duplicate symbol error. Normally, it should be straightforward: We
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; only register labels during first pass and evaluate constants during
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; the second. Easy.
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; We can *almost* do that... but we have ".org". .org affects label
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; values and supports expressions, which means that we have to evaluate
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; constants during first pass. But because we can possibly have forward
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; references in ".equ", some constants are going to have a bad value.
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; Therefore, we really can't evaluate all constants during the first
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; pass.
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; With this situation, how do you manage detection of duplicate symbols?
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; By limiting the "duplicate error" condition to the first pass. During,
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; first pass, sure, we don't have our proper values, but we have all our
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; symbol names. So, if we end up in .alreadyThere during first pass,
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; then it's an error condition. If it's not first pass, then we need
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; to update our value.
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call zasmIsFirstPass
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jr z, .duplicateError
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; Second pass. Don't error out, just update value
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push hl
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ld hl, (SYM_CTX_PTR)
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ex de, hl
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call writeHLinDE
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pop hl
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cp a ; ensure Z
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ret
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.duplicateError:
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ld a, ERR_DUPSYM
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jp unsetZ ; return
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; Select global or local registry according to label name in (HL)
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symSelect:
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call symIsLabelLocal
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jp z, symSelectLocalRegistry
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jp symSelectGlobalRegistry
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; Find name (HL) in (SYM_CTX_NAMES) and make (SYM_CTX_PTR) point to the
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; corresponding entry in (SYM_CTX_VALUES).
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; If we find something, Z is set, otherwise unset.
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symFind:
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push ix
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push hl
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push de
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ex de, hl ; it's easier if HL is haystack and DE is
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; needle.
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ld ix, (SYM_CTX_VALUES)
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ld hl, (SYM_CTX_NAMES)
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.loop:
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call strcmp
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jr z, .match
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; ok, next!
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call _symNext
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jr nz, .nomatch ; end of the chain, nothing found
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inc ix
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inc ix
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jr .loop
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.nomatch:
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call unsetZ
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jr .end
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.match:
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ld (SYM_CTX_PTR), ix
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cp a ; ensure Z
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.end:
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pop de
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pop hl
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pop ix
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ret
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; Return value that (SYM_CTX_PTR) is pointing at in DE.
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symGetVal:
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ld de, (SYM_CTX_PTR)
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jp intoDE
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