Add br_table

br_table is in fact a generalization of other branch types like br or
br_if, since br_table contains several branches for the same pc inside
the nw_lo section.

Therefore, this kind of branch forced some changes to nwp_break and
those relying on it.

8 files changed, 109 insertions, 8 deletions

diff --git a/src/interp/ops.c b/src/interp/ops.c
index 9f80668..4366a49 100644
--- a/src/interp/ops.c
+++ b/src/interp/ops.c
@@ -28,7 +28,7 @@ static void (*const ops[])(struct nw_interp *) =
     nwp_op_end, /* OP_END */
     nwp_op_br, /* OP_BR */
     nwp_op_br_if, /* OP_BR_IF */
-    NULL, /* OP_BR_TABLE */
+    nwp_op_br_table, /* OP_BR_TABLE */
     nwp_op_return, /* OP_RETURN */
     nwp_op_call, /* OP_CALL */
     nwp_op_call_indirect, /* OP_CALL_INDIRECT */
diff --git a/src/op/CMakeLists.txt b/src/op/CMakeLists.txt
index 7468132..7cc6ff8 100644
--- a/src/op/CMakeLists.txt
+++ b/src/op/CMakeLists.txt
@@ -9,6 +9,7 @@ target_sources(${PROJECT_NAME} PRIVATE
     block.c
     br.c
     br_if.c
+    br_table.c
     call.c
     call_indirect.c
     current_memory.c
diff --git a/src/op/br.c b/src/op/br.c
index dd0066f..212d5dd 100644
--- a/src/op/br.c
+++ b/src/op/br.c
@@ -23,7 +23,7 @@ static enum nw_state get_relative_depth(struct nw_interp *const i)
     if (n)
         return n;
 
-    nwp_break(i, b->relative_depth);
+    nwp_break(i, b->relative_depth, 0);
     return NW_AGAIN;
 }
 
diff --git a/src/op/br_if.c b/src/op/br_if.c
index 6eca18a..a413f1e 100644
--- a/src/op/br_if.c
+++ b/src/op/br_if.c
@@ -46,7 +46,7 @@ static enum nw_state pop(struct nw_interp *const i)
     if (n)
         return n;
     else if (condition(i))
-        nwp_break(i, b->relative_depth);
+        nwp_break(i, b->relative_depth, 0);
     else
         nwp_interp_resume(i);
 
diff --git a/src/op/br_table.c b/src/op/br_table.c
new file mode 100644
index 0000000..2737c0d
--- /dev/null
+++ b/src/op/br_table.c
@@ -0,0 +1,98 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nanowasm/nw.h>
+#include <nw/interp.h>
+#include <nw/io.h>
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nw/routines.h>
+#include <nw/stack.h>
+#include <nw/types.h>
+
+static enum nw_state get_target(struct nw_interp *const i)
+{
+    nw_varuint32 target;
+    struct nw_i_sm_br_table *const b = &i->sm.br_table;
+    const struct nw_io_cfg *const cfg = &i->cfg.io;
+    const enum nw_state n = nwp_varuint32(cfg, &b->leb128, &target, cfg->user);
+
+    if (n)
+        return n;
+    else if (b->target_i == b->offset
+        || (!b->set && b->target_i >= b->target_count))
+    {
+        b->set = 1;
+        b->relative_depth = target;
+    }
+
+    if (b->target_i >= b->target_count)
+        nwp_break(i, b->relative_depth, b->offset);
+    else
+        b->target_i++;
+
+    return NW_AGAIN;
+}
+
+static enum nw_state pop(struct nw_interp *const i)
+{
+    struct nw_i_sm_br_table *const b = &i->sm.br_table;
+    const enum nw_state n = nwp_stack_pop(i, &b->io);
+
+    if (n)
+        return n;
+
+    i->next = get_target;
+    return NW_AGAIN;
+}
+
+static enum nw_state get_target_count(struct nw_interp *const i)
+{
+    struct nw_i_sm_br_table *const b = &i->sm.br_table;
+    const struct nw_io_cfg *const cfg = &i->cfg.io;
+    const enum nw_state n = nwp_varuint32(cfg, &b->leb128,
+        &b->target_count, cfg->user);
+    const enum nw_type pt = i->push_type;
+
+    if (n)
+        return n;
+    else if (pt != NW_TYPE_I32)
+    {
+        static const char *const exc = "expected i32 expression for br_table";
+        const char *const stype = nwp_type_str(pt);
+
+        i->exception = exc;
+#ifdef NW_LOG
+        if (stype)
+            nwp_log("%s, got: %s\n", exc, stype);
+        else
+            nwp_log("%s, got: unknown (%#x)\n", exc, (unsigned)pt);
+#endif
+        return NW_FATAL;
+    }
+    else
+    {
+        struct nw_sm_io io = {0};
+
+        io.buf = &b->offset;
+        io.n = sizeof b->offset;
+        b->io = io;
+        i->next = pop;
+    }
+
+    return NW_AGAIN;
+}
+
+void nwp_op_br_table(struct nw_interp *const i)
+{
+    static const struct nw_i_sm_br_table b;
+
+    i->next = get_target_count;
+    i->sm.br_table = b;
+}
diff --git a/src/op/else.c b/src/op/else.c
index 2c1c6b1..13d9c6c 100644
--- a/src/op/else.c
+++ b/src/op/else.c
@@ -14,5 +14,5 @@
 
 void nwp_op_else(struct nw_interp *const i)
 {
-    nwp_break(i, 0);
+    nwp_break(i, 0, 0);
 }
diff --git a/src/op/if.c b/src/op/if.c
index 2ef9565..2f5f4f5 100644
--- a/src/op/if.c
+++ b/src/op/if.c
@@ -25,7 +25,7 @@ static enum nw_state pop(struct nw_interp *const i)
     else if (pif->condition)
         nwp_interp_resume(i);
     else
-        nwp_break(i, 0);
+        nwp_break(i, 0, 0);
 
     return NW_AGAIN;
 }
diff --git a/src/routines/break.c b/src/routines/break.c
index 3ee94a1..bf13ca6 100644
--- a/src/routines/break.c
+++ b/src/routines/break.c
@@ -40,7 +40,7 @@ static enum nw_state skip(struct nw_interp *const i)
 
         i->exception = exc;
 #ifdef NW_LOG
-        nwp_log("%s from offset: %ld\n", exc, b->pc);
+        nwp_log("%s, offset: %#lx\n", exc, b->pc);
 #endif
         return NW_FATAL;
     }
@@ -66,7 +66,7 @@ static enum nw_state get_dst(struct nw_interp *const i)
 
     if (n)
         return n;
-    else if (pc == b->pc)
+    else if (pc == b->pc && b->toffset_i++ >= b->table_offset)
         i->next = seek_dst;
     else
         return skip(i);
@@ -232,12 +232,14 @@ static enum nw_state tell(struct nw_interp *const i)
     return NW_AGAIN;
 }
 
-void nwp_break(struct nw_interp *const i, const nw_varuint32 relative_depth)
+void nwp_break(struct nw_interp *const i, const nw_varuint32 relative_depth,
+    const nw_varuint32 table_offset)
 {
     const struct nw_i_sm_break b = {0};
     struct nw_i_sm_break *const pb = &i->sm.brk;
 
     *pb = b;
     pb->relative_depth = relative_depth;
+    pb->table_offset = table_offset;
     i->next = tell;
 }