Support resumming partial downloads

Julien LepillerMon May 25 21:07:52+0200 2020

b7de40d

Support resumming partial downloads

app/src/main/java/eu/lepiller/nani/DictionaryDownloadActivity.java

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import java.io.OutputStream;
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import java.net.HttpURLConnection;
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import java.net.URL;
27+
import java.util.List;
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import java.util.Map;
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import eu.lepiller.nani.dictionary.Dictionary;
…
178179 
179180 
                    // .sha256 file now downloaded
180181 
                    url = new URL(uri);
182+
                    file = e.getValue();
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                    long expectedLength = -1;
184+
                    boolean acceptRanges = false;
185+
                    if(file.exists()) {
186+
                        // if file exists, it is not fully downloaded, so we check whether we can
187+
                        // do a partial download
188+
                        connection = (HttpURLConnection) url.openConnection();
189+
                        connection.setRequestMethod("HEAD");
190+
                        connection.connect();
191+
                        if(connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
192+
                            expectedLength = connection.getContentLength();
193+
                            acceptRanges = connection.getHeaderFields().containsKey("accept-ranges");
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                            if (acceptRanges) {
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                                List<String> headers = connection.getHeaderFields().get("accept-ranges");
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                                for(String h: headers) {
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                                    if(h.toLowerCase().compareTo("none") == 0)
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                                        acceptRanges = false;
199+
                                }
200+
                            }
201+
                            Log.d(TAG, "Can do range? " + acceptRanges);
202+
                        }
203+
                        output = new FileOutputStream(file, true);
204+
                    } else {
205+
                        output = new FileOutputStream(file);
206+
                    }
207+
208+
                    long total = 0;
181209 
                    connection = (HttpURLConnection) url.openConnection();
210+
                    if(expectedLength > 0 && acceptRanges && file.length() < expectedLength) {
211+
                        connection.addRequestProperty("Range", "bytes=" + file.length() + "-" + (expectedLength-1));
212+
                        total = file.length();
213+
                    }
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                    connection.connect();
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                    // expect HTTP 200 OK, so we don't mistakenly save error report
185217 
                    // instead of the file
186-
                    if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
218+
                    if (connection.getResponseCode() != HttpURLConnection.HTTP_OK &&
219+
                            connection.getResponseCode() != HttpURLConnection.HTTP_PARTIAL) {
187220 
                        Log.e(TAG, "Server returned HTTP " + connection.getResponseCode()
188221 
                                + " " + connection.getResponseMessage());
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                        return "Server returned HTTP " + connection.getResponseCode()
…
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197230 
                    // download the file
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                    input = connection.getInputStream();
199-
                    file = e.getValue();
200-
                    output = new FileOutputStream(file);
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202-
                    long total = 0;
203233 
                    while ((count = input.read(data)) != -1) {
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                        // allow canceling with back button
205235 
                        if (isCancelled()) {