# The OS/K Team licenses this file to you under the MIT license.
# See the LICENSE file in the project root for more information.

#---------------------------------------------------------------------------#
# String manipulation instructions                                          #
#---------------------------------------------------------------------------#

#
# Store value into string (STOSx)
#
#       [%1] = $2
#       IF (DF == 0) THEN
#           %str = %str + sizeof(x)
#       ELSE
#           %str = %str - sizeof(x)
#       FI
#
# When no parameters are given, %str = RDI and $val = RAX
# When one parameter is given, %str = RDI and $val = $1
# When two parameters are given, %str = $1 and $val = $2
#
stosb r ri
stosw r ri
stosl r ri
stosq r ri

#
# Load value from string (LODSx)
#
#       $1 = [%2]
#       IF (DF == 0) THEN
#           %str = %str + sizeof(x)
#       ELSE
#           %str = %str - sizeof(x)
#       FI
#
# Preserves CF, OF and SF
# Sets ZF according to the loaded value
#
lodsb r r
lodsw r r
lodsl r r
lodsq r r

#
# Scan string for a particular value (SCASx)
#
#       CMP([%1], $2)
#
#       IF ([%1] == 0) THEN
#           ZF = 1
#       ELIF (ZF == 0) THEN
#           IF (DF == 0) THEN
#               %1 = %1 + sizeof(x)
#           ELSE
#               %1 = %1 - sizeof(x)
#           FI
#       FI
#
# Sets CF, OF and SF according to the result of the comparison
# Sets ZF according to whether [%1] and $2 are equal, OR if [%1] is null
#
# Notes:
# - Does not move past the value when found
# - 'SCASB.REP.NZ reg ch' is a short 'strchnul()'
#
scasb r ri
scasw r ri
scasl r ri
scasq r ri

#
# Compare bytes in strings (CMPSx)
#
#       CMP([%1], [%2])
#
#       IF (DF == 0) THEN
#           %1 = %1 + sizeof(x)
#           %2 = %2 + sizeof(x)
#       ELSE
#           %1 = %1 - sizeof(x)
#           %2 = %2 - sizeof(x)
#       FI
#
# Sets CF, OF, ZF and SF according to the result of the comparison
#
# Moves past the compared values in any case!
#
cmpsb r r
cmpsw r r
cmpsl r r
cmpsq r r

#
# Safe compare bytes in strings (CMPZSx)
#
# Behaves precisely like CMPSx, except in the following case:
#   - If both [%1] and [%2] are zero, clears ZF (indicating NOT EQUAL)
#
# This prevents 'CMPZSx.REP.Z' from looping infinitely when both strings
# have the exact same content; this allows for short strcmp's
#
cmpzsb r r
cmpzsw r r
cmpzsl r r
cmpzsq r r

#
# Move value from string to string (MOVSx)
#
#       [%1] = [%1]
#       IF (DF == 0) THEN
#           %1 = %1 + sizeof(x)
#           %2 = %2 + sizeof(x)
#       ELSE
#           %1 = %1 - sizeof(x)
#           %2 = %2 - sizeof(x)
#       FI
#
# Preserves CF, OF and SF
# Sets ZF according to the moved value
#
movsb r r
movsw r r
movsl r r
movsq r r

#---------------------------------------------------------------------------#