/**
* Read the python preamble off of stderr. It ends when the prompy '>>> ' is detected.
*
* @return the preamble read from stderr
*/
private String readPreamble(int timeoutMs) {
String rv = null;
StringBuilder sb = new StringBuilder();
long timeout = System.currentTimeMillis() + timeoutMs;
try {
char[] prompt = {'>', '>', '>', ' '};
int index = 0;
while (true) {
// sleep until there's input
while (!stderr.ready()) {
Thread.yield();
if (timeoutMs >= 0 && System.currentTimeMillis() >= timeout)
error("Timeout (" + timeoutMs + " ms) reached while reading python preamble.");
}
int readInt = stderr.read();
if (readInt == -1) // end of stream
error("End of output stream was reached while looking for python prompt.");
char c = (char) readInt;
sb.append(c);
if (c == prompt[index]) {
++index;
if (index == prompt.length) {
// exit only if there are no more bytes to be read
if (!stderr.ready()) break;
else index = 0;
}
} else index = 0;
}
// trim off the prompt
int len = sb.length();
sb.delete(len - prompt.length, len);
// remove \n and \r if they're at the end of the string
trimSuffix(sb, '\n');
trimSuffix(sb, '\r');
rv = sb.toString();
} catch (IOException e) {
error("Error while reading python preamble.", e);
}
return rv;
}
/**
* Read stdout until the prompt '>>> ' is given on stderr
*
* @param quitOnStderr should we raise an exception if stderr output is detected other than the
* prompt?
* @return output the received stdout / stderr strings
*/
private String readUntilPrompt() {
String rv = null;
StringBuilder sbStdout = new StringBuilder();
StringBuilder sbStderr = new StringBuilder();
long timeout = System.currentTimeMillis() + timeoutMs;
try {
char[] prompt = {'>', '>', '>', ' '};
int index = 0;
boolean done = false;
while (!done) {
// sleep until there's input
while (!stdout.ready() && !stderr.ready()) {
Thread.yield();
if (timeoutMs >= 0 && System.currentTimeMillis() >= timeout) {
String out = "";
String err = "";
if (sbStdout.length() > 0) out = "\nStdout was: '" + sbStdout.toString() + "'";
if (sbStderr.length() > 0) err = "\nStderr was: '" + sbStderr.toString() + "'";
error("Timeout (" + timeoutMs + " ms) reached during python interaction." + out + err);
}
}
// read stdout until blocked
while (stdout.ready()) {
int readInt = stdout.read();
if (readInt == -1) // end of stream
error("End of output stream was reached while reading python response.");
sbStdout.append((char) readInt);
}
// read stderr until blocked
while (stderr.ready()) {
int readInt = stderr.read();
if (readInt == -1) // end of stream
error("End of output stream was reached while looking for python prompt.");
char c = (char) readInt;
sbStderr.append(c);
if (c == prompt[index]) {
++index;
if (index == prompt.length) {
// exit only if there are no more bytes to be read
if (!stderr.ready()) {
done = true;
break;
} else index = 0;
}
} else index = 0;
}
}
// read any remaining stdout characters
sbStdout.append(readUntilBlocked(stdout));
// trim off the prompt
sbStderr.delete(sbStderr.length() - prompt.length, sbStderr.length());
// trim off \n if it's at the end
trimSuffix(sbStdout, '\n');
trimSuffix(sbStdout, '\r');
// if anything was printed to stderr, it's an error
if (sbStderr.length() > 0)
error(
"Python produced output on stderr:\n'"
+ sbStderr.toString()
+ "'"
+ (sbStdout.length() > 0 ? "\n\nstdout was:\n" + sbStdout.toString() : ""));
rv = sbStdout.toString();
} catch (IOException e) {
error("Error while reading python output", e);
}
return rv;
}