ref: a411870ee4640241e3c494367d922847da84f972
dir: /appl/cmd/mash/symb.b/
# # Symbol table routines. A symbol table becomes copy-on-write # when it is cloned. The first modification will copy the hash table. # Every list is then copied on first modification. # # # Copy a hash list. # cpsymbs(l: list of ref Symb): list of ref Symb { r: list of ref Symb; while (l != nil) { r = (ref *hd l) :: r; l = tl l; } return r; } # # New symbol table. # Stab.new(): ref Stab { return ref Stab(array[SHASH] of list of ref Symb, 0, 0); } # # Clone a symbol table. Copy Stab and mark contents copy-on-write. # Stab.clone(t: self ref Stab): ref Stab { t.copy = 1; t.wmask = SMASK; return ref *t; } # # Update symbol table entry, or add new entry. # Stab.update(t: self ref Stab, s: string, tag: int, v: list of string, f: ref Cmd, b: Mashbuiltin): ref Symb { if (t.copy) { a := array[SHASH] of list of ref Symb; a[:] = t.tab[:]; t.tab = a; t.copy = 0; } x := hash->fun1(s, SHASH); l := t.tab[x]; if (t.wmask & (1 << x)) { l = cpsymbs(l); t.tab[x] = l; t.wmask &= ~(1 << x); } r := l; while (r != nil) { h := hd r; if (h.name == s) { case tag { Svalue => h.value = v; Sfunc => h.func = f; Sbuiltin => h.builtin = b; } return h; } r = tl r; } n := ref Symb(s, v, f, b, 0); t.tab[x] = n :: l; return n; } # # Make a list of a symbol table's contents. # Stab.all(t: self ref Stab): list of ref Symb { r: list of ref Symb; for (i := 0; i < SHASH; i++) { for (l := t.tab[i]; l != nil; l = tl l) r = (ref *hd l) :: r; } return r; } # # Assign a list of strings to a variable. The distinguished value # "empty" is used to distinguish nil value from undefined. # Stab.assign(t: self ref Stab, s: string, v: list of string) { if (v == nil) v = empty; t.update(s, Svalue, v, nil, nil); } # # Define a builtin. # Stab.defbuiltin(t: self ref Stab, s: string, b: Mashbuiltin) { t.update(s, Sbuiltin, nil, nil, b); } # # Define a function. # Stab.define(t: self ref Stab, s: string, f: ref Cmd) { t.update(s, Sfunc, nil, f, nil); } # # Symbol table lookup. # Stab.find(t: self ref Stab, s: string): ref Symb { l := t.tab[hash->fun1(s, SHASH)]; while (l != nil) { h := hd l; if (h.name == s) return h; l = tl l; } return nil; } # # Function lookup. # Stab.func(t: self ref Stab, s: string): ref Cmd { v := t.find(s); if (v == nil) return nil; return v.func; } # # New environment. # Env.new(): ref Env { return ref Env(Stab.new(), nil, ETop, nil, nil, nil, nil, nil, nil, 0); } # # Clone environment. No longer top-level or interactive. # Env.clone(e: self ref Env): ref Env { e = e.copy(); e.flags &= ~(ETop | EInter); e.global = e.global.clone(); if (e.local != nil) e.local = e.local.clone(); return e; } # # Copy environment. # Env.copy(e: self ref Env): ref Env { return ref *e; } # # Fetch $n argument. # Env.arg(e: self ref Env, s: string): string { n := int s; if (e.args == nil || n >= len e.args) return "$" + s; else return e.args[n]; } # # Lookup builtin. # Env.builtin(e: self ref Env, s: string): Mashbuiltin { v := e.global.find(s); if (v == nil) return nil; return v.builtin; } # # Define a builtin. # Env.defbuiltin(e: self ref Env, s: string, b: Mashbuiltin) { e.global.defbuiltin(s, b); } # # Define a function. # Env.define(e: self ref Env, s: string, f: ref Cmd) { e.global.define(s, f); } # # Value of a shell variable (check locals then globals). # Env.dollar(e: self ref Env, s: string): ref Symb { if (e.local != nil) { l := e.local.find(s); if (l != nil && l.value != nil) return l; } g := e.global.find(s); if (g != nil && g.value != nil) return g; return nil; } # # Lookup a function. # Env.func(e: self ref Env, s: string): ref Cmd { v := e.global.find(s); if (v == nil) return nil; return v.func; } # # Local assignment. # Env.let(e: self ref Env, s: string, v: list of string) { if (e.local == nil) e.local = Stab.new(); e.local.assign(s, v); } # # Assignment. Update local or define global. # Env.set(e: self ref Env, s: string, v: list of string) { if (e.local != nil && e.local.find(s) != nil) e.local.assign(s, v); else e.global.assign(s, v); } # # Report undefined. # Env.undefined(e: self ref Env, s: string) { e.report(s + ": undefined"); }