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This commit is contained in:
folex 2019-08-15 15:19:57 +03:00
parent 391e9b1d34
commit b54b030698
1 changed files with 19 additions and 5 deletions
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24
rust-workshop/step3-finished-app/src/database.rs
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@ -4,27 +4,35 @@ use crate::api::AppResult;
use crate::errors::err_msg;
use crate::ffi;
// Execute query on SQLite
pub fn query(query: String) -> AppResult<String> {
log::debug!("executing query: '{}'", query);
unsafe {
let bytes = query.as_bytes();
let query_ptr = ffi::allocate(bytes.len());
// Convert query string to bytes
let query_bytes = query.as_bytes();
// Allocate memory for query in SQLite module
let query_ptr = ffi::allocate(query_bytes.len());
for (i, byte) in bytes.iter().enumerate() {
// Store query in SQLite's memory
for (i, byte) in query_bytes.iter().enumerate() {
let ptr = query_ptr + i as i32;
ffi::store(ptr, *byte);
}
let result_ptr = ffi::invoke(query_ptr, bytes.len());
// Execute the query, and get pointer to the result
let result_ptr = ffi::invoke(query_ptr, query_bytes.len());
// First 4 bytes at result_ptr location encode result size, read that first
let mut result_size: usize = 0;
for i in 0..3 {
let ptr = result_ptr + i as i32;
let b = ffi::load(ptr) as usize;
result_size = result_size + (b << (8 * i));
}
// Now we know exact size of the query execution result
// Read query execution result byte-by-byte
let mut result_bytes = vec![0; result_size as usize];
for i in 4..(result_size + 4) {
let ptr = result_ptr + i as i32;
@ -32,11 +40,17 @@ pub fn query(query: String) -> AppResult<String> {
result_bytes[i as usize - 4] = b;
}
// Deallocate query result
ffi::deallocate(result_ptr, result_size + 4);
// Decode query result to a utf8 string
let result_str = std::str::from_utf8(result_bytes.as_slice());
// Log if there's an error
if result_str.is_err() {
log::error!("unable to decode result from bytes: {:#x?}", result_bytes);
}
// Wrap error with a better message, and return Result
result_str
.map_err(|e| {
err_msg(&format!(