/*
* Get the next line.
* A "current" position is passed and a "new" position is returned.
* The current position is the position of the first character of
* a line. The new position is the position of the first character
* of the NEXT line. The line obtained is the line starting at curr_pos.
*/
off_t
forw_line(off_t curr_pos)
{
off_t new_pos;
int c;
if (curr_pos == NULL_POSITION || ch_seek(curr_pos))
return (NULL_POSITION);
c = ch_forw_get();
if (c == EOI)
return (NULL_POSITION);
prewind();
for (;;) {
if (sigs)
return (NULL_POSITION);
if (c == '\n' || c == EOI) {
/*
* End of the line.
*/
new_pos = ch_tell();
break;
}
/*
* Append the char to the line and get the next char.
*/
if (pappend(c)) {
/*
* The char won't fit in the line; the line
* is too long to print in the screen width.
* End the line here.
*/
new_pos = ch_tell() - 1;
break;
}
c = ch_forw_get();
}
(void) pappend('\0');
if (squeeze && *line == '\0') {
/*
* This line is blank.
* Skip down to the last contiguous blank line
* and pretend it is the one which we are returning.
*/
while ((c = ch_forw_get()) == '\n')
if (sigs)
return (NULL_POSITION);
if (c != EOI)
(void) ch_back_get();
new_pos = ch_tell();
}
return (new_pos);
}
/*
* Get the previous line.
* A "current" position is passed and a "new" position is returned.
* The current position is the position of the first character of
* a line. The new position is the position of the first character
* of the PREVIOUS line. The line obtained is the one starting at new_pos.
*/
off_t
back_line(off_t curr_pos)
{
off_t new_pos, begin_new_pos;
int c;
if (curr_pos == NULL_POSITION || curr_pos <= (off_t)0 ||
ch_seek(curr_pos-1))
return (NULL_POSITION);
if (squeeze) {
/*
* Find out if the "current" line was blank.
*/
(void) ch_forw_get(); /* Skip the newline */
c = ch_forw_get(); /* First char of "current" line */
(void) ch_back_get(); /* Restore our position */
(void) ch_back_get();
if (c == '\n') {
/*
* The "current" line was blank.
* Skip over any preceeding blank lines,
* since we skipped them in forw_line().
*/
while ((c = ch_back_get()) == '\n')
if (sigs)
return (NULL_POSITION);
if (c == EOI)
return (NULL_POSITION);
(void) ch_forw_get();
}
}
/*
* Scan backwards until we hit the beginning of the line.
*/
for (;;) {
if (sigs)
return (NULL_POSITION);
c = ch_back_get();
if (c == '\n') {
/*
* This is the newline ending the previous line.
* We have hit the beginning of the line.
*/
new_pos = ch_tell() + 1;
break;
}
if (c == EOI) {
/*
* We have hit the beginning of the file.
* This must be the first line in the file.
* This must, of course, be the beginning of the line.
*/
new_pos = ch_tell();
break;
}
}
/*
* Now scan forwards from the beginning of this line.
* We keep discarding "printable lines" (based on screen width)
* until we reach the curr_pos.
*
* {{ This algorithm is pretty inefficient if the lines
* are much longer than the screen width,
* but I don't know of any better way. }}
*/
if (ch_seek(new_pos))
return (NULL_POSITION);
loop:
begin_new_pos = new_pos;
prewind();
do {
c = ch_forw_get();
if (c == EOI || sigs)
return (NULL_POSITION);
new_pos++;
if (c == '\n')
break;
if (pappend(c)) {
/*
* Got a full printable line, but we haven't
* reached our curr_pos yet. Discard the line
* and start a new one.
*/
(void) pappend('\0');
(void) ch_back_get();
new_pos--;
goto loop;
}
} while (new_pos < curr_pos);
(void) pappend('\0');
return (begin_new_pos);
}
swexp_list_node *parse_block(parser *p) {
// parses a block of lines with the same indentation into a chain
// (not a list)
char c;
swexp_list_node fakehead, *tail;
fakehead.next = NULL;
fakehead.content = NULL;
fakehead.type = UNDEFINED;
tail = &fakehead;
// get initial indentation by consuming characters until we find some
unsigned int current_indentation;
for (current_indentation = p->indentation; is_space(pgetc(p));
current_indentation++) {
}
prewind(p, '\0');
while ((c = pgetc(p)) != EOF) {
// if we encounter a comment in any state, strip it out
IGNORE_COMMENTS()
switch (p->state) {
case COUNTING_INDENTATION:
if (is_space(c)) {
p->indentation++;
} else if (is_newline(c)) {
p->indentation = 0;
} else {
// this is a start of an atom.
// parse as appropriate based on indent
prewind(p, c);
if (p->indentation > current_indentation) {
if (tail->type == ATOM) {
// make the tail a list before appending
swexp_list_node *tailcont = malloc(sizeof(swexp_list_node));
tailcont->type = ATOM;
tailcont->next = NULL;
tailcont->content = tail->content;
tailcont->location = NULL;
tail->type = LIST;
tail->content = tailcont;
if (tail->location != NULL) {
free(tail->location);
tail->location = NULL;
}
}
// append it to the list that is the last
// element
list_tail(tail)->next = parse_block(p);
} else if (p->indentation == current_indentation) {
tail->next = parse_line(p);
p->state = COUNTING_INDENTATION;
tail = tail->next;
} else {
goto clean_and_return;
}
}
break;
default:
printf("unexpected state in parse_line\n");
exit(1);
}
}
clean_and_return:
return fakehead.next;
}
swexp_list_node *parse_s_expr(parser *p, char opening_brace) {
char c;
swexp_list_node fakehead, *tail = &fakehead;
fakehead.next = NULL;
fakehead.content = NULL;
fakehead.type = UNDEFINED;
char closing_brace = brace_pair(opening_brace);
while ((c = pgetc(p)) != EOF && !is_closing_brace(c)) {
// if we encounter a comment in any state, strip it out
IGNORE_COMMENTS()
switch (p->state) {
case SKIP_SPACE:
if (is_space(c) || is_newline(c)) {
// do nothing if it is space or newline
} else if (is_opening_brace(c)) {
// parse the parenthesized s expression into a list
// and append it to the thing
swexp_list_node *list = malloc(sizeof(swexp_list_node));
list->type = LIST;
list->next = NULL;
list->location = NULL;
list->content = parse_s_expr(p, c);
tail->next = list;
tail = list;
} else {
// step back and start collecting the atom
prewind(p, c);
begin_atom(p);
}
break;
case COLLECTING_ATOM:
if (is_space(c) || is_newline(c)) {
prewind(p, c);
tail->next = close_atom(p);
tail = tail->next;
} else if (is_opening_brace(c)) {
swexp_list_node *node = close_atom(p);
node->next = parse_s_expr(p, c);
tail->next = listof(node);
tail = chain_tail(tail);
} else {
build_atom(p, c);
}
break;
default:
printf("unexpected state %d in parse_s_expr", p->state);
exit(1);
}
}
if (is_closing_brace(c) && c != closing_brace) {
printf("mismatched braces in s expression\n");
exit(1);
}
if (p->state == COLLECTING_ATOM) {
tail->next = close_atom(p);
}
if (c == EOF) {
printf("unexpected EOF while parsing s expression\n");
exit(1);
}
p->state = SKIP_SPACE;
return fakehead.next;
}
swexp_list_node *parse_line(parser *p) {
// parses a line of text, starting at a non-whitespace char
char c;
// build a list of expressions started by this
// list head on the stack.
swexp_list_node head, *tail;
head.next = NULL;
head.content = NULL;
head.type = UNDEFINED;
tail = &head;
p->state = SKIP_SPACE;
while ((c = pgetc(p)) != EOF && !is_newline(c) && !is_closing_brace(c)) {
// if we encounter a comment in any state, strip it out
IGNORE_COMMENTS()
switch (p->state) {
case COLLECTING_ATOM:
if (is_space(c)) {
// end atom
tail->next = close_atom(p);
tail = tail->next;
prewind(p, c);
} else if (is_opening_brace(c)) {
swexp_list_node *bracehead = close_atom(p);
swexp_list_node *bracecontent = parse_s_expr(p, c);
bracehead->next = bracecontent;
tail->next = listof(bracehead);
tail = chain_tail(tail);
} else {
// continue to build item
build_atom(p, c);
}
break;
case SKIP_SPACE:
if (is_opening_brace(c)) {
swexp_list_node *brace = parse_s_expr(p, c);
tail->next = brace;
tail = chain_tail(tail);
} else if (!is_space(c)) {
begin_atom(p);
prewind(p, c);
}
break;
default:
printf("unexpected state %d in parse_line\n", p->state);
exit(1);
}
}
if (is_newline(c)) {
p->indentation = 0;
}
if (is_closing_brace(c)) {
printf("encountered unmatched closing brace\n");
exit(1);
}
// close ongoing capture
if (p->state == COLLECTING_ATOM) {
tail->next = close_atom(p);
}
// if the number of collected atoms is more than one,
// make it a list and return it
if (chain_len(head.next) > 1) {
swexp_list_node *listhead = malloc(sizeof(swexp_list_node));
listhead->type = LIST;
listhead->next = NULL;
listhead->content = head.next;
listhead->location = NULL;
return listhead;
} else {
return head.next;
}
}
