CS 330 Lecture 19 – Abstracting a GUI
Agenda
- the libexpat API
- slurping a file in C
- adding a GUI abstraction layer using XML
TODO
- Why we chunk-read: http://java.sun.com/developer/technicalArticles/Programming/PerfTuning/
- C file I/O: http://en.wikibooks.org/wiki/A_Little_C_Primer/C_File-IO_Through_Library_Functions
Code
parse_xml.c
#include <expat.h>
#include <stdio.h>
#include <stdlib.h>
/* typedef parser_t * XML_Parser; */
/* ------------------------------------------------------------------------- */
void start(void *data,
const char *tag,
const char **attributes) {
printf("data: %d\n", *((int *) data));
printf("tag: %s\n", tag);
}
/* ------------------------------------------------------------------------- */
void end(void *data,
const char *tag) {
printf("tag: %s\n", tag);
}
/* ------------------------------------------------------------------------- */
int main(int argc, char **argv) {
int foo = 17;
XML_Parser parser = XML_ParserCreate(NULL);
XML_SetElementHandler(parser, start, end);
XML_SetUserData(parser, &foo);
FILE *xml_file = fopen(argv[1], "r");
int done = 0;
const int BUFFER_SIZE = 8192;
char buffer[BUFFER_SIZE];
while (!done) {
int length = fread(buffer, sizeof(char), BUFFER_SIZE, xml_file);
done = feof(xml_file);
XML_Parse(parser, buffer, length, done);
}
fclose(xml_file);
XML_ParserFree(parser);
return 0;
}
emailclient.xml
<?xml version="1.0" encoding="UTF-8"?> <panel orientation="vertical"> <panel orientation="horizontal"> <label text="To:" /> <textbox name="toBox" /> </panel> <panel orientation="horizontal"> <label text="Subject:" /> <textbox name="subjectBox" /> </panel> <textarea name="bodyBox" /> <button text="Send" /> </panel>
swingify.c
#include <expat.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int coreyNeedsToThinkOfAName = -1;
/* ------------------------------------------------------------------------- */
void start(void *data,
const char *tag,
const char **attributes) {
/* printf("open %s\n", tag); */
/* for (int i = 0; attributes[i] != NULL; i += 2) { */
/* printf("%s -> %s\n", attributes[i], attributes[i + 1]); */
/* } */
if (strcmp(tag, "panel") == 0) {
++coreyNeedsToThinkOfAName;
printf("JPanel panel%d = new JPanel();\n", coreyNeedsToThinkOfAName);
printf("panel%d.setLayout(new BoxLayout(panel%d, BoxLayout.%s));\n", coreyNeedsToThinkOfAName, coreyNeedsToThinkOfAName, strcmp(attributes[1], "vertical") == 0 ? "PAGE_AXIS" : "LINE_AXIS");
} else if (strcmp(tag, "label") == 0) {
printf("panel%d.add(new JLabel(\"%s\"));\n", coreyNeedsToThinkOfAName, attributes[1]);
} else if (strcmp(tag, "textbox") == 0) {
printf("panel%d.add(new JTextField());\n", coreyNeedsToThinkOfAName);
}
}
/* ------------------------------------------------------------------------- */
void end(void *data,
const char *tag) {
/* printf("close %s\n", tag); */
}
/* ------------------------------------------------------------------------- */
int main(int argc, char **argv) {
XML_Parser parser = XML_ParserCreate(NULL);
XML_SetElementHandler(parser, start, end);
FILE *xml_file = fopen(argv[1], "r");
int done = 0;
const int BUFFER_SIZE = 8192;
char buffer[BUFFER_SIZE];
while (!done) {
int length = fread(buffer, sizeof(char), BUFFER_SIZE, xml_file);
done = feof(xml_file);
XML_Parse(parser, buffer, length, done);
}
fclose(xml_file);
XML_ParserFree(parser);
return 0;
}
Haiku
Gramps says life was tough.
Read and write XML much?
That’s uphill both ways.
Read and write XML much?
That’s uphill both ways.