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get C macro values from the compiler #7

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get C macro values from the compiler #7

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38 changes: 31 additions & 7 deletions src/main/java/net/smacke/jaydio/OpenFlags.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,20 +15,44 @@
*/
package net.smacke.jaydio;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.stream.Collectors;

/**
* Constants for {@link DirectIoLib#oDirectOpen(String, boolean)}. </p>
*
* @author smacke
*
*/
public final class OpenFlags {
public static final int O_RDONLY = 00;
public static final int O_WRONLY = 01;
public static final int O_RDWR = 02;
public static final int O_CREAT = 0100;
public static final int O_TRUNC = 01000;
public static final int O_DIRECT = 040000;
public static final int O_SYNC = 04000000;
public static final int O_RDONLY = getOpenFlags("O_RDONLY");
public static final int O_WRONLY = getOpenFlags("O_WRONLY");
public static final int O_RDWR = getOpenFlags("O_RDWR");
public static final int O_CREAT = getOpenFlags("O_CREAT");
public static final int O_TRUNC = getOpenFlags("O_TRUNC");
public static final int O_DIRECT = getOpenFlags("O_DIRECT");
public static final int O_SYNC = getOpenFlags("O_SYNC");

private OpenFlags() {}

private static int getOpenFlags(final String s) {
try {
final Process pb = new ProcessBuilder("/bin/sh", "-c",
"printf \"%d\" $(printf '#include<fcntl.h>\\n" + s + "' | gcc -D_GNU_SOURCE -E - | tail -n1)")
.redirectErrorStream(true).start();
final List<String> collect;
try (BufferedReader br = new BufferedReader(new InputStreamReader(pb.getInputStream(), StandardCharsets.UTF_8))) {
collect = br.lines().collect(Collectors.toList());
}
if (pb.waitFor() != 0 || collect.size() != 1)
throw new RuntimeException("Cannot get C macro " + s + " " + collect);
return Integer.parseInt(collect.get(0));
} catch (IOException | InterruptedException e) {
throw new RuntimeException("Cannot get C macro " + s, e);
}
}
}