extendr_api/io/
save.rs

1//! Wrapper for R output streams.
2
3use super::PstreamFormat;
4use crate::{catch_r_error, error::Error, error::Result, robj::GetSexp, throw_r_error};
5use extendr_ffi::{
6    R_NilValue, R_Serialize, R_outpstream_st, R_outpstream_t, R_pstream_data_t, R_pstream_format_t,
7    SEXP,
8};
9use std::io::Write;
10
11/// The hook will convert some objects into strings.
12pub struct WriteHook {
13    pub func: unsafe extern "C" fn(arg1: SEXP, arg2: SEXP) -> SEXP,
14    pub data: SEXP,
15}
16
17pub struct OutStream<W: Write> {
18    r_state: R_outpstream_st,
19    writer: W,
20}
21
22impl<W: Write> OutStream<W> {
23    pub fn from_writer(
24        writer: W,
25        format: PstreamFormat,
26        version: i32,
27        hook: Option<WriteHook>,
28    ) -> Box<OutStream<W>> {
29        unsafe extern "C" fn outchar<W: Write>(arg1: R_outpstream_t, arg2: ::std::os::raw::c_int) {
30            let writer = &mut *((*arg1).data as *mut W);
31            let b = [arg2 as u8];
32            if let Err(e) = writer.write_all(&b) {
33                throw_r_error(format!("failed to write R serialization stream: {e}"));
34            }
35        }
36
37        unsafe extern "C" fn outbytes<W: Write>(
38            arg1: R_outpstream_t,
39            arg2: *mut ::std::os::raw::c_void,
40            arg3: ::std::os::raw::c_int,
41        ) {
42            let writer = &mut *((*arg1).data as *mut W);
43            let b = std::slice::from_raw_parts(arg2 as *mut u8, arg3 as usize);
44            if let Err(e) = writer.write_all(b) {
45                throw_r_error(format!("failed to write R serialization stream: {e}"));
46            }
47        }
48
49        {
50            let (hook_fn, hook_data) = if let Some(WriteHook { func, data }) = hook {
51                (Some(func), data)
52            } else {
53                unsafe { (None, R_NilValue) }
54            };
55
56            let r_state = extendr_ffi::R_outpstream_st {
57                data: std::ptr::null_mut(),
58                type_: format as R_pstream_format_t,
59                version,
60                OutChar: Some(outchar::<W>),
61                OutBytes: Some(outbytes::<W>),
62                OutPersistHookFunc: hook_fn,
63                OutPersistHookData: hook_data,
64            };
65            let mut os = Box::new(OutStream { r_state, writer });
66            os.r_state.data = &mut os.writer as *mut W as R_pstream_data_t;
67            os
68        }
69    }
70}
71
72pub trait Save: GetSexp {
73    /// Save an object in the R data format.
74    /// `version` should probably be 3.
75    fn save<P: AsRef<std::path::Path>>(
76        &self,
77        path: &P,
78        format: PstreamFormat,
79        version: i32,
80        hook: Option<WriteHook>,
81    ) -> Result<()> {
82        let mut writer = std::fs::File::create(path.as_ref())
83            .map_err(|_| Error::Other(format!("could not create file {:?}", path.as_ref())))?;
84        self.to_writer(&mut writer, format, version, hook)
85    }
86
87    /// Save an object in the R data format to a `Write` trait.
88    /// `version` should probably be 3.
89    fn to_writer<W: Write>(
90        &self,
91        writer: &mut W,
92        format: PstreamFormat,
93        version: i32,
94        hook: Option<WriteHook>,
95    ) -> Result<()> {
96        let mut os = OutStream::from_writer(writer, format, version, hook);
97
98        let stream = &mut os.r_state as R_outpstream_t;
99        let sexp = unsafe { self.get() };
100        if !(2..=3).contains(&version) {
101            return Err(Error::Other(format!(
102                "version must be 2 or 3, got {:?}",
103                version
104            )));
105        }
106
107        catch_r_error(move || unsafe {
108            R_Serialize(sexp, stream);
109            R_NilValue
110        })?;
111        Ok(())
112    }
113}
114
115impl<R: GetSexp> Save for R {}
extendr_api/io/save.rs

extendr_api/io/
save.rs
