1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150

use std::io::{Read, Seek};
use std::sync::Arc;

use snafu::OptionExt;

use self::column::Column;
use self::decompress::Decompressor;
use self::metadata::{read_metadata, read_stripe_footer, FileMetadata};
use self::schema::{create_schema, TypeDescription};
use crate::error::{self, Result};
use crate::proto::{StripeFooter, StripeInformation};

pub mod arrow;
mod column;
pub mod decode;
pub mod decompress;
pub mod metadata;
pub mod schema;

pub struct Reader<R: Read + Seek> {
    inner: R,
    metadata: Box<FileMetadata>,
    schema: Arc<TypeDescription>,
}

impl<R: Read + Seek> Reader<R> {
    pub fn new(mut r: R) -> Result<Self> {
        let metadata = Box::new(read_metadata(&mut r)?);
        let schema = create_schema(&metadata.footer.types, 0)?;

        Ok(Self {
            inner: r,
            metadata,
            schema,
        })
    }

    pub fn metadata(&self) -> &FileMetadata {
        &self.metadata
    }

    pub fn schema(&self) -> &TypeDescription {
        &self.schema
    }

    pub fn select(self, fields: &[&str]) -> Result<Cursor<R>> {
        Cursor::new(self, fields)
    }

    pub fn stripe(&self, index: usize) -> Option<StripeInformation> {
        self.metadata.footer.stripes.get(index).cloned()
    }

    pub fn stripe_footer(&mut self, stripe: usize) -> Result<StripeFooter> {
        read_stripe_footer(&mut self.inner, &self.metadata, stripe, &mut vec![])
    }
}

pub struct Cursor<R: Read + Seek> {
    reader: Reader<R>,
    columns: Vec<(String, Arc<TypeDescription>)>,
    stripe_offset: usize,
}

impl<R: Read + Seek> Cursor<R> {
    pub fn new<T: AsRef<str>>(r: Reader<R>, fields: &[T]) -> Result<Self> {
        let mut columns = Vec::with_capacity(fields.len());
        for name in fields {
            let field = r
                .schema
                .field(name.as_ref())
                .context(error::FieldNotFOundSnafu {
                    name: name.as_ref(),
                })?;
            columns.push((name.as_ref().to_string(), field));
        }
        Ok(Self {
            reader: r,
            columns,
            stripe_offset: 0,
        })
    }

    pub fn root(r: Reader<R>) -> Result<Self> {
        let root = &r.metadata().footer.types[0];
        let fields = &root.field_names.clone();
        Self::new(r, fields)
    }
}

impl<R: Read + Seek> Iterator for Cursor<R> {
    type Item = Result<Stripe>;

    fn next(&mut self) -> Option<Self::Item> {
        if let Some(info) = self.reader.stripe(self.stripe_offset) {
            let stripe = Stripe::new(&mut self.reader, &self.columns, self.stripe_offset, info);

            self.stripe_offset += 1;

            Some(stripe)
        } else {
            None
        }
    }
}

#[derive(Debug)]
pub struct Stripe {
    footer: Arc<StripeFooter>,
    columns: Vec<Column>,
    stripe_offset: usize,
    info: StripeInformation,
}

impl Stripe {
    pub fn new<R: Read + Seek>(
        r: &mut Reader<R>,
        columns: &[(String, Arc<TypeDescription>)],
        stripe: usize,
        info: StripeInformation,
    ) -> Result<Self> {
        let footer = Arc::new(r.stripe_footer(stripe)?);

        let compression = r.metadata().postscript.compression();
        //TODO(weny): add tz
        let columns = columns
            .iter()
            .map(|(name, typ)| Column::new(r, compression, name, typ, &footer, &info))
            .collect::<Result<Vec<_>>>()?;

        Ok(Self {
            footer,
            columns,
            stripe_offset: stripe,
            info,
        })
    }

    pub fn footer(&self) -> &Arc<StripeFooter> {
        &self.footer
    }

    pub fn stripe_offset(&self) -> usize {
        self.stripe_offset
    }

    pub fn stripe_info(&self) -> &StripeInformation {
        &self.info
    }
}