io/buffered/reader.fz
# This file is part of the Fuzion language implementation.
#
# The Fuzion language implementation is free software: you can redistribute it
# and/or modify it under the terms of the GNU General Public License as published
# by the Free Software Foundation, version 3 of the License.
#
# The Fuzion language implementation is distributed in the hope that it will be
# useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
# License for more details.
#
# You should have received a copy of the GNU General Public License along with The
# Fuzion language implementation. If not, see <https://www.gnu.org/licenses/>.
# -----------------------------------------------------------------------
#
# Tokiwa Software GmbH, Germany
#
# Source code of Fuzion standard library feature io.buffered.reader
#
# -----------------------------------------------------------------------
# buffered.reader effect allows buffered reading
# by using the given Read_Provider
#
# note: anything in the buffer when effect is uninstalled will be discarded.
#
public reader(private rp Read_Provider, buf_size i32, buffer array u8 | io.end_of_file) : effect effect_mode.plain is
# install this effect and execute 'f'. Wrap the result of 'f' into an
# 'outcome' if 'f' returns normally, otherwise if 'f' is aborted early
# via a call to 'raise' wrap the 'error' passed to 'raise' into the
# resulting 'outcome'.
#
public with(R type, f ()->R) outcome R =>
try reader R (() -> run f (() -> exit 1))
# terminate immediately with the given error wrapped in 'option'.
#
raise(e error) =>
(try reader).env.raise e
# read returns the current buffer or end of file.
# in case the buffer is empty it fills the buffer
# before returning it.
#
public read => read buf_size
# read returns the current buffer or end of file.
# in case the buffer is empty it fills the buffer
# with up to max_n bytes before returning it.
#
public read(max_n i32) array u8 | io.end_of_file
post result ? io.end_of_file => true | a array => !a.is_empty
=>
match buffer
b array =>
if b.is_empty
fill_buffer max_n
buffer
io.end_of_file => io.end_of_file
# fill the currently empty buffer with up to max_n bytes
#
private fill_buffer(max_n i32)
pre match buffer
a array => a.is_empty
io.end_of_file => false
is
match rp.read max_n
a array =>
set buffer := a
replace
eof io.end_of_file =>
set buffer := eof
replace
e error => raise e
# discard n items from buffer
#
public discard(n i32)
pre n >= 0
is
match buffer
b array =>
set buffer := (b.slice n b.length).as_array
replace
io.end_of_file =>
# discard complete buffer
#
# NYI naming this feature discard leads to error: Duplicate feature declaration
public discard_all
is
match buffer
b array =>
set buffer := []
replace
io.end_of_file =>
# short hand for getting the currently installed `buffered.reader`
#
reader =>
io.buffered.reader.env
# read n bytes using the currently installed byte reader effect
# if the returned sequence is empty or count is less than n, end of file has been reached.
#
public read_bytes(n i32) Sequence u8 ! reader =>
mi : mutate is
mi.go ()->
res := (mutate.array u8).new mi
for n_read := 0, n_read + r
while n_read < n
r := match reader.read # NYI: we should limit the number of byted read by reader.read, we can exceed n!
io.end_of_file => -1
a (array u8) =>
reader.discard a.length
for b in a do
res.add b
a.length
until r < 0
res.as_array
# read string, up to n codepoints or until end of file
# requires `buffered.reader` effect to be installed.
#
public read_string(n i32) String ! reader
pre n >= 0
=>
take_valid_codepoints(a Sequence u8, max i32) =>
v := String.from_bytes a
.codepoints_and_errors
.take_while x->
match x
codepoint => true
error => false
.take max
.map String x->
match x
c codepoint => c
error => exit 1
.as_array
bytes_used := (v.map c->c.as_string.byte_length).fold i32.sum
reader.discard bytes_used
v
for
is_eof := reader.read ? io.end_of_file => true | a array => false
next_bytes Sequence u8 := (reader.read ? io.end_of_file => [] | a array => a), rest ++ (reader.read ? io.end_of_file => [] | a array => a)
next_codepoints := take_valid_codepoints next_bytes n, take_valid_codepoints next_bytes n-codepoint_count
# if we did not use any bytes and `next_bytes` contains not enough bytes for a codepoint potentially,
# we trigger a `discard_all` and remember what we read so far via `rest`.
# this is necesarry e.g. for stdin where we read one byte at a time.
rest Sequence u8 := if n>0 && next_codepoints.is_empty && next_bytes.count < 4 then reader.discard_all; next_bytes else []
codepoint_count := next_codepoints.count, codepoint_count+next_codepoints.count
res Sequence String := next_codepoints, res ++ next_codepoints
while !is_eof && codepoint_count < n
else
if is_eof && res.is_empty
reader.raise (error "-- end of file --"); ""
else
String.join res
# use the currently installed byte reader effect
# to read until a line feed occurs.
# returns the line
#
public read_line String|io.end_of_file ! reader =>
if reader.read ? io.end_of_file => true | * => false
io.end_of_file
else
mi : mutate is
mi.go String ()->
res := (mutate.array u8).new mi
while
match reader.read
io.end_of_file =>
false
a array =>
# trailing carriage returns are dropped
add_to_res(a Sequence u8) is
if !a.is_empty
a1 := if a.last = character_encodings.ascii.cr
(a.slice 0 a.count-1)
else
a
for b in a1 do
res.add b
match (container.searchable_sequence a).index_of character_encodings.ascii.lf
idx i32 =>
add_to_res (a.slice 0 idx)
reader.discard idx+1
false
nil =>
add_to_res a
reader.discard_all
true
ref : String
utf8 Sequence u8 := res.as_array
# Read input fully into an array of bytes until end_of_file is reached
#
public read_fully array u8 ! reader =>
for
r Sequence u8 := [], r++n
n := (io.buffered.read_bytes 8192)
while n.count > 0 else
r.as_array
# Read input fully and split it at linefeed (ASCII 10) characters. Delete
# any trailing carriage returns (ASCII 13) from the resulting strings.
#
public read_lines array String ! reader =>
(String.from_bytes read_fully).split "\n"
.map s->
s.ends_with "\r" ? TRUE => s.substring 0 s.byte_length-1
| FALSE => s
.as_array
last changed: 2024-03-07