prog8/compiler/res/prog8lib/virtual/string.p8
Irmen de Jong f2d27403c5 add string.endswith() to efficiently test for a suffix without copying
add string.startswith() to efficiently test for string prefix without copying
2022-07-21 00:38:30 +02:00

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; 0-terminated string manipulation routines. For the Virtual Machine target.
string {
sub length(str st) -> ubyte {
; Returns the number of bytes in the string.
; This value is determined during runtime and counts upto the first terminating 0 byte in the string,
; regardless of the size of the string during compilation time. Dont confuse this with len and sizeof!
ubyte count = 0
while st[count]
count++
return count
}
sub left(str source, ubyte slen, str target) {
; Copies the left side of the source string of the given length to target string.
; It is assumed the target string buffer is large enough to contain the result.
; Also, you have to make sure yourself that length is smaller or equal to the length of the source string.
; Modifies in-place, doesnt return a value (so cant be used in an expression).
target[slen] = 0
ubyte ix
for ix in 0 to slen-1 {
target[ix] = source[ix]
}
}
sub right(str source, ubyte slen, str target) {
; Copies the right side of the source string of the given length to target string.
; It is assumed the target string buffer is large enough to contain the result.
; Also, you have to make sure yourself that length is smaller or equal to the length of the source string.
; Modifies in-place, doesnt return a value (so cant be used in an expression).
ubyte offset = length(source)-slen
ubyte ix
for ix in 0 to slen-1 {
target[ix] = source[ix+offset]
}
target[ix]=0
}
sub slice(str source, ubyte start, ubyte slen, str target) {
; Copies a segment from the source string, starting at the given index,
; and of the given length to target string.
; It is assumed the target string buffer is large enough to contain the result.
; Also, you have to make sure yourself that start and length are within bounds of the strings.
; Modifies in-place, doesnt return a value (so cant be used in an expression).
ubyte ix
for ix in 0 to slen-1 {
target[ix] = source[ix+start]
}
target[ix]=0
}
sub find(str st, ubyte character) -> ubyte {
; Locates the first position of the given character in the string,
; returns Carry set if found + index in A, or Carry clear if not found.
ubyte ix
for ix in 0 to length(st)-1 {
if st[ix]==character {
sys.set_carry()
return ix
}
}
sys.clear_carry()
return 0
}
sub copy(str source, str target) -> ubyte {
; Copy a string to another, overwriting that one.
; Returns the length of the string that was copied.
; Often you dont have to call this explicitly and can just write string1 = string2
; but this function is useful if youre dealing with addresses for instance.
ubyte ix
repeat {
ubyte char=source[ix]
target[ix]=char
if not char
return ix
ix++
}
}
sub compare(str st1, str st2) -> byte {
; Compares two strings for sorting.
; Returns -1 (255), 0 or 1 depending on wether string1 sorts before, equal or after string2.
; Note that you can also directly compare strings and string values with eachother using
; comparison operators ==, < etcetera (it will use strcmp for you under water automatically).
return prog8_lib.string_compare(st1, st2)
}
sub lower(str st) -> ubyte {
; Lowercases the petscii string in-place. Returns length of the string.
; (for efficiency, non-letter characters > 128 will also not be left intact,
; but regular text doesn't usually contain those characters anyway.)
ubyte ix
repeat {
ubyte char=st[ix]
if not char
return ix
if char >= 'A' and char <= 'Z'
st[ix] = char | %00100000
ix++
}
}
sub upper(str st) -> ubyte {
; Uppercases the petscii string in-place. Returns length of the string.
ubyte ix
repeat {
ubyte char=st[ix]
if not char
return ix
if char >= 97 and char <= 122
st[ix] = char & %11011111
ix++
}
}
sub startswith(str st, str prefix) -> bool {
ubyte prefix_len = length(prefix)
ubyte str_len = length(st)
if prefix_len > str_len
return false
cx16.r9L = st[prefix_len]
st[prefix_len] = 0
cx16.r9H = compare(st, prefix) as ubyte
st[prefix_len] = cx16.r9L
return cx16.r9H==0
}
sub endswith(str st, str suffix) -> bool {
ubyte suffix_len = length(suffix)
ubyte str_len = length(st)
if suffix_len > str_len
return false
return compare(st + str_len - suffix_len, suffix) == 0
}
}