exif 0.0.1

Rust wrapper for libexif
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use std::ffi::CString;
use std::slice;

use libc::{self, c_char, c_uint};

use exif_sys::*;

use tag::Tag;
use value::Value;
use bits::*;
use internal::*;

/// Data found in a single EXIF tag.
pub struct Entry<'a> {
    inner: &'a mut ExifEntry,
}

impl<'a> FromLibExif<&'a mut ExifEntry> for Entry<'a> {
    fn from_libexif(entry: &'a mut ExifEntry) -> Self {
        Entry { inner: entry }
    }
}

impl<'a> Entry<'a> {
    /// EXIF tag for the entry.
    pub fn tag(&self) -> Tag {
        Tag::from_libexif(self.inner.tag)
    }

    /// Type of data contained in the entry.
    pub fn data_type(&self) -> DataType {
        DataType::from_libexif(self.inner.format)
    }

    /// Number of data elements in the entry.
    pub fn components(&self) -> usize {
        self.inner.components as usize
    }

    /// Return the raw binary data for the entry's value.
    pub fn raw_data(&self) -> &[u8] {
        unsafe {
            slice::from_raw_parts(self.inner.data,
                                  self.inner.size as usize)
        }
    }

    /// Returns an interpreted value of the entry's data.
    pub fn value(&self, byte_order: ByteOrder) -> Value {
        Value::extract(self.raw_data(), self.data_type(), self.components(), byte_order)
    }

    /// Returns a textual representation of the entry's data.
    pub fn text_value(&self) -> String {
        let mut buffer = Vec::<u8>::with_capacity(256);

        let cstring =
            unsafe {
                let len = libc::strlen(exif_entry_get_value(self.inner as *const _ as *mut _,
                                                            buffer.as_mut_ptr() as *mut c_char,
                                                            buffer.capacity() as c_uint));

                buffer.set_len(len);

                CString::from_vec_unchecked(buffer)
            };

        cstring.into_string().expect("invalid UTF-8")
    }
}