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upscheme/femtolisp/read.c

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C
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enum {
TOK_NONE, TOK_OPEN, TOK_CLOSE, TOK_DOT, TOK_QUOTE, TOK_SYM, TOK_NUM,
TOK_BQ, TOK_COMMA, TOK_COMMAAT, TOK_COMMADOT,
TOK_SHARPDOT, TOK_LABEL, TOK_BACKREF, TOK_SHARPQUOTE, TOK_SHARPOPEN,
TOK_OPENB, TOK_CLOSEB, TOK_SHARPSYM, TOK_GENSYM, TOK_DOUBLEQUOTE
};
// defines which characters are ordinary symbol characters.
// exceptions are '.', which is an ordinary symbol character
// unless it's the only character in the symbol, and '#', which is
// an ordinary symbol character unless it's the first character.
static int symchar(char c)
{
static char *special = "()[]'\";`,\\|";
return (!isspace(c) && !strchr(special, c));
}
static int isnumtok(char *tok, value_t *pval)
{
char *end;
int64_t i64;
uint64_t ui64;
double d;
if (*tok == '\0')
return 0;
if (!((tok[0]=='0' && tok[1]=='x') || // these formats are always integer
(tok[0]=='0' && isdigit(tok[1]))) &&
strpbrk(tok, ".eE")) {
d = strtod(tok, &end);
if (*end == '\0') {
if (pval) *pval = mk_double(d);
return 1;
}
if (end > tok && *end == 'f' && end[1] == '\0') {
if (pval) *pval = mk_float((float)d);
return 1;
}
}
if (isdigit(tok[0]) || tok[0]=='-' || tok[0]=='+') {
if (tok[0]=='-') {
i64 = strtoll(tok, &end, 0);
if (pval) *pval = return_from_int64(i64);
}
else {
ui64 = strtoull(tok, &end, 0);
if (pval) *pval = return_from_uint64(ui64);
}
if (*end == '\0')
return 1;
}
return 0;
}
static u_int32_t toktype = TOK_NONE;
static value_t tokval;
static char buf[256];
static char nextchar(ios_t *f)
{
int ch;
char c;
do {
ch = ios_getc(f);
if (ch == IOS_EOF)
return 0;
c = (char)ch;
if (c == ';') {
// single-line comment
do {
ch = ios_getc(f);
if (ch == IOS_EOF)
return 0;
} while ((char)ch != '\n');
c = (char)ch;
}
} while (isspace(c));
return c;
}
static void take(void)
{
toktype = TOK_NONE;
}
static void accumchar(char c, int *pi)
{
buf[(*pi)++] = c;
if (*pi >= (int)(sizeof(buf)-1))
lerror(ParseError, "read: token too long");
}
// return: 1 if escaped (forced to be symbol)
static int read_token(ios_t *f, char c, int digits)
{
int i=0, ch, escaped=0, issym=0, first=1;
while (1) {
if (!first) {
ch = ios_getc(f);
if (ch == IOS_EOF)
goto terminate;
c = (char)ch;
}
first = 0;
if (c == '|') {
issym = 1;
escaped = !escaped;
}
else if (c == '\\') {
issym = 1;
ch = ios_getc(f);
if (ch == IOS_EOF)
goto terminate;
accumchar((char)ch, &i);
}
else if (!escaped && !(symchar(c) && (!digits || isdigit(c)))) {
break;
}
else {
accumchar(c, &i);
}
}
ios_ungetc(c, f);
terminate:
buf[i++] = '\0';
return issym;
}
static u_int32_t peek(ios_t *f)
{
char c, *end;
fixnum_t x;
int ch;
if (toktype != TOK_NONE)
return toktype;
c = nextchar(f);
if (ios_eof(f)) return TOK_NONE;
if (c == '(') {
toktype = TOK_OPEN;
}
else if (c == ')') {
toktype = TOK_CLOSE;
}
else if (c == '[') {
toktype = TOK_OPENB;
}
else if (c == ']') {
toktype = TOK_CLOSEB;
}
else if (c == '\'') {
toktype = TOK_QUOTE;
}
else if (c == '`') {
toktype = TOK_BQ;
}
else if (c == '"') {
toktype = TOK_DOUBLEQUOTE;
}
else if (c == '#') {
ch = ios_getc(f);
if (ch == IOS_EOF)
lerror(ParseError, "read: invalid read macro");
if ((char)ch == '.') {
toktype = TOK_SHARPDOT;
}
else if ((char)ch == '\'') {
toktype = TOK_SHARPQUOTE;
}
else if ((char)ch == '\\') {
uint32_t cval;
if (ios_getutf8(f, &cval) == IOS_EOF)
lerror(ParseError, "read: end of input in character constant");
toktype = TOK_NUM;
tokval = fixnum(cval);
if (cval > 0x7f) {
tokval = cvalue_wchar(&tokval, 1);
}
else {
tokval = cvalue_char(&tokval, 1);
}
}
else if ((char)ch == '(') {
toktype = TOK_SHARPOPEN;
}
else if ((char)ch == '<') {
lerror(ParseError, "read: unreadable object");
}
else if (isdigit((char)ch)) {
read_token(f, (char)ch, 1);
c = (char)ios_getc(f);
if (c == '#')
toktype = TOK_BACKREF;
else if (c == '=')
toktype = TOK_LABEL;
else
lerror(ParseError, "read: invalid label");
errno = 0;
x = strtol(buf, &end, 10);
if (*end != '\0' || errno)
lerror(ParseError, "read: invalid label");
tokval = fixnum(x);
}
else if ((char)ch == '!') {
// #! single line comment for shbang script support
do {
ch = ios_getc(f);
} while (ch != IOS_EOF && (char)ch != '\n');
return peek(f);
}
else if ((char)ch == '|') {
// multiline comment
while (1) {
ch = ios_getc(f);
hashpipe_got:
if (ch == IOS_EOF)
lerror(ParseError, "read: eof within comment");
if ((char)ch == '|') {
ch = ios_getc(f);
if ((char)ch == '#')
break;
goto hashpipe_got;
}
}
// this was whitespace, so keep peeking
return peek(f);
}
else if ((char)ch == ':') {
// gensym
ch = ios_getc(f);
if ((char)ch == 'g')
ch = ios_getc(f);
read_token(f, (char)ch, 0);
errno = 0;
x = strtol(buf, &end, 10);
if (*end != '\0' || buf[0] == '\0' || errno)
lerror(ParseError, "read: invalid gensym label");
toktype = TOK_GENSYM;
tokval = fixnum(x);
}
else if (symchar((char)ch)) {
read_token(f, ch, 0);
toktype = TOK_SHARPSYM;
tokval = symbol(buf);
c = nextchar(f);
if (c != '(') {
take();
lerror(ParseError, "read: expected argument list for %s",
symbol_name(tokval));
}
}
else {
lerror(ParseError, "read: unknown read macro");
}
}
else if (c == ',') {
toktype = TOK_COMMA;
ch = ios_getc(f);
if (ch == IOS_EOF)
return toktype;
if ((char)ch == '@')
toktype = TOK_COMMAAT;
else if ((char)ch == '.')
toktype = TOK_COMMADOT;
else
ios_ungetc((char)ch, f);
}
else {
if (!read_token(f, c, 0)) {
if (buf[0]=='.' && buf[1]=='\0') {
return (toktype=TOK_DOT);
}
else {
errno = 0;
if (isnumtok(buf, &tokval)) {
if (errno)
lerror(ParseError,"read: overflow in numeric constant");
return (toktype=TOK_NUM);
}
}
}
toktype = TOK_SYM;
tokval = symbol(buf);
}
return toktype;
}
static value_t do_read_sexpr(ios_t *f, value_t label);
static value_t read_vector(ios_t *f, value_t label, u_int32_t closer)
{
value_t v=alloc_vector(4, 1), elt;
u_int32_t i=0;
PUSH(v);
if (label != UNBOUND)
ptrhash_put(&readstate->backrefs, (void*)label, (void*)v);
while (peek(f) != closer) {
if (ios_eof(f))
lerror(ParseError, "read: unexpected end of input");
if (i >= vector_size(v))
Stack[SP-1] = vector_grow(v);
elt = do_read_sexpr(f, UNBOUND);
v = Stack[SP-1];
vector_elt(v,i) = elt;
i++;
}
take();
vector_setsize(v, i);
return POP();
}
static value_t read_string(ios_t *f)
{
char *buf, *temp;
char eseq[10];
size_t i=0, j, sz = 64, ndig;
int c;
value_t s;
u_int32_t wc;
buf = malloc(sz);
while (1) {
if (i >= sz-4) { // -4: leaves room for longest utf8 sequence
sz *= 2;
temp = realloc(buf, sz);
if (temp == NULL) {
free(buf);
lerror(ParseError, "read: out of memory reading string");
}
buf = temp;
}
c = ios_getc(f);
if (c == IOS_EOF) {
free(buf);
lerror(ParseError, "read: unexpected end of input in string");
}
if (c == '"')
break;
else if (c == '\\') {
c = ios_getc(f);
if (c == IOS_EOF) {
free(buf);
lerror(ParseError, "read: end of input in escape sequence");
}
j=0;
if (octal_digit(c)) {
do {
eseq[j++] = c;
c = ios_getc(f);
} while (octal_digit(c) && j<3 && (c!=IOS_EOF));
if (c!=IOS_EOF) ios_ungetc(c, f);
eseq[j] = '\0';
wc = strtol(eseq, NULL, 8);
i += u8_wc_toutf8(&buf[i], wc);
}
else if ((c=='x' && (ndig=2)) ||
(c=='u' && (ndig=4)) ||
(c=='U' && (ndig=8))) {
c = ios_getc(f);
while (hex_digit(c) && j<ndig && (c!=IOS_EOF)) {
eseq[j++] = c;
c = ios_getc(f);
}
if (c!=IOS_EOF) ios_ungetc(c, f);
eseq[j] = '\0';
if (j) wc = strtol(eseq, NULL, 16);
else {
free(buf);
lerror(ParseError, "read: invalid escape sequence");
}
i += u8_wc_toutf8(&buf[i], wc);
}
else {
buf[i++] = read_escape_control_char((char)c);
}
}
else {
buf[i++] = c;
}
}
s = cvalue_string(i);
memcpy(cvalue_data(s), buf, i);
free(buf);
return s;
}
// build a list of conses. this is complicated by the fact that all conses
// can move whenever a new cons is allocated. we have to refer to every cons
// through a handle to a relocatable pointer (i.e. a pointer on the stack).
static void read_list(ios_t *f, value_t *pval, value_t label)
{
value_t c, *pc;
u_int32_t t;
PUSH(NIL);
pc = &Stack[SP-1]; // to keep track of current cons cell
t = peek(f);
while (t != TOK_CLOSE) {
if (ios_eof(f))
lerror(ParseError, "read: unexpected end of input");
c = mk_cons(); car_(c) = cdr_(c) = NIL;
if (iscons(*pc)) {
cdr_(*pc) = c;
}
else {
*pval = c;
if (label != UNBOUND)
ptrhash_put(&readstate->backrefs, (void*)label, (void*)c);
}
*pc = c;
c = do_read_sexpr(f,UNBOUND); // must be on separate lines due to
car_(*pc) = c; // undefined evaluation order
t = peek(f);
if (t == TOK_DOT) {
take();
c = do_read_sexpr(f,UNBOUND);
cdr_(*pc) = c;
t = peek(f);
if (ios_eof(f))
lerror(ParseError, "read: unexpected end of input");
if (t != TOK_CLOSE)
lerror(ParseError, "read: expected ')'");
}
}
take();
(void)POP();
}
// label is the backreference we'd like to fix up with this read
static value_t do_read_sexpr(ios_t *f, value_t label)
{
value_t v, sym, oldtokval, *head;
value_t *pv;
u_int32_t t;
t = peek(f);
take();
switch (t) {
case TOK_CLOSE:
lerror(ParseError, "read: unexpected ')'");
case TOK_CLOSEB:
lerror(ParseError, "read: unexpected ']'");
case TOK_DOT:
lerror(ParseError, "read: unexpected '.'");
case TOK_SYM:
case TOK_NUM:
return tokval;
case TOK_COMMA:
head = &COMMA; goto listwith;
case TOK_COMMAAT:
head = &COMMAAT; goto listwith;
case TOK_COMMADOT:
head = &COMMADOT; goto listwith;
case TOK_BQ:
head = &BACKQUOTE; goto listwith;
case TOK_QUOTE:
head = &QUOTE;
listwith:
v = cons_reserve(2);
car_(v) = *head;
cdr_(v) = tagptr(((cons_t*)ptr(v))+1, TAG_CONS);
car_(cdr_(v)) = cdr_(cdr_(v)) = NIL;
PUSH(v);
if (label != UNBOUND)
ptrhash_put(&readstate->backrefs, (void*)label, (void*)v);
v = do_read_sexpr(f,UNBOUND);
car_(cdr_(Stack[SP-1])) = v;
return POP();
case TOK_SHARPQUOTE:
// femtoLisp doesn't need symbol-function, so #' does nothing
return do_read_sexpr(f, label);
case TOK_OPEN:
PUSH(NIL);
read_list(f, &Stack[SP-1], label);
return POP();
case TOK_SHARPSYM:
// constructor notation
sym = tokval;
PUSH(NIL);
read_list(f, &Stack[SP-1], UNBOUND);
v = POP();
return apply(symbol_value(sym), v);
case TOK_OPENB:
return read_vector(f, label, TOK_CLOSEB);
case TOK_SHARPOPEN:
return read_vector(f, label, TOK_CLOSE);
case TOK_SHARPDOT:
// eval-when-read
// evaluated expressions can refer to existing backreferences, but they
// cannot see pending labels. in other words:
// (... #2=#.#0# ... ) OK
// (... #2=#.(#2#) ... ) DO NOT WANT
v = do_read_sexpr(f,UNBOUND);
return toplevel_eval(v);
case TOK_LABEL:
// create backreference label
if (ptrhash_has(&readstate->backrefs, (void*)tokval))
lerror(ParseError, "read: label %ld redefined", numval(tokval));
oldtokval = tokval;
v = do_read_sexpr(f, tokval);
ptrhash_put(&readstate->backrefs, (void*)oldtokval, (void*)v);
return v;
case TOK_BACKREF:
// look up backreference
v = (value_t)ptrhash_get(&readstate->backrefs, (void*)tokval);
if (v == (value_t)PH_NOTFOUND)
lerror(ParseError, "read: undefined label %ld", numval(tokval));
return v;
case TOK_GENSYM:
pv = (value_t*)ptrhash_bp(&readstate->gensyms, (void*)tokval);
if (*pv == (value_t)PH_NOTFOUND)
*pv = gensym(NULL, 0);
return *pv;
case TOK_DOUBLEQUOTE:
return read_string(f);
}
return NIL;
}
value_t read_sexpr(ios_t *f)
{
value_t v;
readstate_t state;
state.prev = readstate;
ptrhash_new(&state.backrefs, 16);
ptrhash_new(&state.gensyms, 16);
readstate = &state;
v = do_read_sexpr(f, UNBOUND);
readstate = state.prev;
free_readstate(&state);
return v;
}
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