nostrdb

monster.c (15096B)

---

 // Example on how to build a Monster FlatBuffer.
 
 
 // Note: while some older C89 compilers are supported when
 // -DFLATCC_PORTABLE is defined, this particular sample is known not to
 // not work with MSVC 2010 (MSVC 2013 is OK) due to inline variable
 // declarations. These are easily move to the start of code blocks, but
 // since we follow the step-wise tutorial, it isn't really practical
 // in this case. The comment style is technically also in violation of C89.
 
 
 #include "monster_builder.h" // Generated by `flatcc`.
 // <string.h> and <assert.h> already included.
 
 // Convenient namespace macro to manage long namespace prefix.
 // The ns macro makes it possible to write `ns(Monster_create(...))`
 // instead of `MyGame_Sample_Monster_create(...)`
 #undef ns
 #define ns(x) FLATBUFFERS_WRAP_NAMESPACE(MyGame_Sample, x) // Specified in the schema.
 
 // A helper to simplify creating vectors from C-arrays.
 #define c_vec_len(V) (sizeof(V)/sizeof((V)[0]))
 
 // This allows us to verify result in optimized builds.
 #define test_assert(x) do { if (!(x)) { assert(0); return -1; }} while(0)
 
 // Bottom-up approach where we create child objects and store these
 // in temporary references before a parent object is created with
 // these references.
 int create_monster_bottom_up(flatcc_builder_t *B, int flexible)
 {
     flatbuffers_string_ref_t weapon_one_name = flatbuffers_string_create_str(B, "Sword");
     int16_t weapon_one_damage = 3;
 
     flatbuffers_string_ref_t weapon_two_name = flatbuffers_string_create_str(B, "Axe");
     int16_t weapon_two_damage = 5;
 
     // Use the `MyGame_Sample_Weapon_create` shortcut to create Weapons
     // with all the fields set.
     //
     // In the C-API, verbs (here create) always follow the type name
     // (here Weapon), prefixed by the namespace (here MyGame_Sample_):
     // MyGame_Sample_Weapon_create(...), or ns(Weapone_create(...)).
     ns(Weapon_ref_t) sword = ns(Weapon_create(B, weapon_one_name, weapon_one_damage));
     ns(Weapon_ref_t) axe = ns(Weapon_create(B, weapon_two_name, weapon_two_damage));
 
     // Serialize a name for our monster, called "Orc".
     // The _str suffix indicates the source is an ascii-z string.
     flatbuffers_string_ref_t name = flatbuffers_string_create_str(B, "Orc");
 
     // Create a `vector` representing the inventory of the Orc. Each number
     // could correspond to an item that can be claimed after he is slain.
     uint8_t treasure[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
     flatbuffers_uint8_vec_ref_t inventory;
     // `c_vec_len` is the convenience macro we defined earlier.
     inventory = flatbuffers_uint8_vec_create(B, treasure, c_vec_len(treasure));
 
     // Here we use a top-down approach locally to build a Weapons vector
     // in-place instead of creating a temporary external vector to use
     // as argument like we did with the `inventory` earlier on, but the
     // overall approach is still bottom-up.
     ns(Weapon_vec_start(B));
     ns(Weapon_vec_push(B, sword));
     ns(Weapon_vec_push(B, axe));
     ns(Weapon_vec_ref_t) weapons = ns(Weapon_vec_end(B));
 
 
     // Create a `Vec3`, representing the Orc's position in 3-D space.
     ns(Vec3_t) pos = { 1.0f, 2.0f, 3.0f };
 
 
     // Set his hit points to 300 and his mana to 150.
     int16_t hp = 300;
     // The default value is 150, so we will never store this field.
     int16_t mana = 150;
 
     // Create the equipment union. In the C++ language API this is given
     // as two arguments to the create call, or as two separate add
     // operations for the type and the table reference. Here we create
     // a single union value that carries both the type and reference.
     ns(Equipment_union_ref_t) equipped = ns(Equipment_as_Weapon(axe));
 
     if (!flexible) {
         // Finally, create the monster using the `Monster_create` helper function
         // to set all fields.
         //
         // Note that the Equipment union only take up one argument in C, where
         // C++ takes a type and an object argument.
         ns(Monster_create_as_root(B, &pos, mana, hp, name, inventory, ns(Color_Red),
                              weapons, equipped));
 
         // Unlike C++ we do not use a Finish call. Instead we use the
         // `create_as_root` action which has better type safety and
         // simplicity.
         //
         // However, we can also express this as:
         //
         // ns(Monster_ref_t) orc = ns(Monster_create(B, ...));
         // flatcc_builder_buffer_create(orc);
         //
         // In this approach the function should return the orc and
         // let a calling function handle the flatcc_buffer_create call
         // for a more composable setup that is also able to create child
         // monsters. In general, `flatcc_builder` calls are best isolated
         // in a containing driver function.
 
     } else {
 
         // A more flexible approach where we mix bottom-up and top-down
         // style. We still create child objects first, but then create
         // a top-down style monster object that we can manipulate in more
         // detail.
 
         // It is important to pair `start_as_root` with `end_as_root`.
         ns(Monster_start_as_root(B));
         ns(Monster_pos_create(B, 1.0f, 2.0f, 3.0f));
         // or alternatively
         //ns(Monster_pos_add(&pos);
 
         ns(Monster_hp_add(B, hp));
         // Notice that `Monser_name_add` adds a string reference unlike the
         // add_str and add_strn variants.
         ns(Monster_name_add(B, name));
         ns(Monster_inventory_add(B, inventory));
         ns(Monster_color_add(B, ns(Color_Red)));
         ns(Monster_weapons_add(B, weapons));
         ns(Monster_equipped_add(B, equipped));
         // Complete the monster object and make it the buffer root object.
         ns(Monster_end_as_root(B));
 
         // We could also drop the `as_root` suffix from Monster_start/end(B)
         // and add the table as buffer root later:
         //
         // ns(Monster_ref_t) orc = ns(Monster_start(B));
         // ...
         // ns(Monster_ref_t) orc = ns(Monster_end(B));
         // flatcc_builder_buffer_create(orc);
         //
         // It is best to keep the `flatcc_builder` calls in a containing
         // driver function for modularity.
     }
     return 0;
 }
 
 // Alternative top-down approach where parent objects are created before
 // their children. We only need to save one reference because the `axe`
 // object is used in two places effectively making the buffer object
 // graph a DAG.
 int create_monster_top_down(flatcc_builder_t *B)
 {
     uint8_t treasure[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
     size_t treasure_count = c_vec_len(treasure);
     ns(Weapon_ref_t) axe;
 
     // NOTE: if we use end_as_root, we MUST also start as root.
     ns(Monster_start_as_root(B));
     ns(Monster_pos_create(B, 1.0f, 2.0f, 3.0f));
     ns(Monster_hp_add(B, 300));
     //ns(Monster_mana_add(B, 150));
     // We use create_str instead of add because we have no existing string reference.
     ns(Monster_name_create_str(B, "Orc"));
     // Again we use create because we no existing vector object, only a C-array.
     ns(Monster_inventory_create(B, treasure, treasure_count));
     ns(Monster_color_add(B, ns(Color_Red)));
     if (1) {
         ns(Monster_weapons_start(B));
         ns(Monster_weapons_push_create(B, flatbuffers_string_create_str(B, "Sword"), 3));
         // We reuse the axe object later. Note that we dereference a pointer
         // because push always returns a short-term pointer to the stored element.
         // We could also have created the axe object first and simply pushed it.
         axe = *ns(Monster_weapons_push_create(B, flatbuffers_string_create_str(B, "Axe"), 5));
         ns(Monster_weapons_end(B));
     } else {
         // We can have more control with the table elements added to a vector:
         //
         ns(Monster_weapons_start(B));
         ns(Monster_weapons_push_start(B));
         ns(Weapon_name_create_str(B, "Sword"));
         ns(Weapon_damage_add(B, 3));
         ns(Monster_weapons_push_end(B));
         ns(Monster_weapons_push_start(B));
         ns(Weapon_name_create_str(B, "Axe"));
         ns(Weapon_damage_add(B, 5));
         axe = *ns(Monster_weapons_push_end(B));
         ns(Monster_weapons_end(B));
     }
     // Unions can get their type by using a type-specific add/create/start method.
     ns(Monster_equipped_Weapon_add(B, axe));
 
     ns(Monster_end_as_root(B));
     return 0;
 }
 
 // This isn't strictly needed because the builder already included the reader,
 // but we would need it if our reader were in a separate file.
 #include "monster_reader.h"
 
 #undef ns
 #define ns(x) FLATBUFFERS_WRAP_NAMESPACE(MyGame_Sample, x) // Specified in the schema.
 
 int access_monster_buffer(const void *buffer)
 {
     // Note that we use the `table_t` suffix when reading a table object
     // as opposed to the `ref_t` suffix used during the construction of
     // the buffer.
     ns(Monster_table_t) monster = ns(Monster_as_root(buffer));
 
     // Note: root object pointers are NOT the same as the `buffer` pointer.
 
     // Make sure the buffer is accessible.
     test_assert(monster != 0);
 
     int16_t hp = ns(Monster_hp(monster));
     int16_t mana = ns(Monster_mana(monster));
     // This is just a const char *, but it also supports a fast length operation.
     flatbuffers_string_t name = ns(Monster_name(monster));
     size_t name_len = flatbuffers_string_len(name);
 
     test_assert(hp == 300);
     // Since 150 is the default, we are reading a value that wasn't stored.
     test_assert(mana == 150);
     test_assert(0 == strcmp(name, "Orc"));
     test_assert(name_len == strlen("Orc"));
 
     int hp_present = ns(Monster_hp_is_present(monster)); // 1
     int mana_present = ns(Monster_mana_is_present(monster)); // 0
     test_assert(hp_present);
     test_assert(!mana_present);
 
     ns(Vec3_struct_t) pos = ns(Monster_pos(monster));
     // Make sure pos has been set.
     test_assert(pos != 0);
     float x = ns(Vec3_x(pos));
     float y = ns(Vec3_y(pos));
     float z = ns(Vec3_z(pos));
 
     // The literal `f` suffix is important because double literals does
     // not always map cleanly to 32-bit represention even with only a few digits:
     // `1.0 == 1.0f`, but `3.2 != 3.2f`.
     test_assert(x == 1.0f);
     test_assert(y == 2.0f);
     test_assert(z == 3.0f);
 
     // We can also read the position into a C-struct. We have to copy
     // because we generally do not know if the native endian format
     // matches the one stored in the buffer (pe: protocol endian).
     ns(Vec3_t) pos_vec;
     // `pe` indicates endian conversion from protocol to native.
     ns(Vec3_copy_from_pe(&pos_vec, pos));
     test_assert(pos_vec.x == 1.0f);
     test_assert(pos_vec.y == 2.0f);
     test_assert(pos_vec.z == 3.0f);
 
     // This is a const uint8_t *, but it shouldn't be accessed directly
     // to ensure proper endian conversion. However, uint8 (ubyte) are
     // not sensitive endianness, so we *could* have accessed it directly.
     // The compiler likely optimizes this so that it doesn't matter.
     flatbuffers_uint8_vec_t inv = ns(Monster_inventory(monster));
     size_t inv_len = flatbuffers_uint8_vec_len(inv);
     // Make sure the inventory has been set.
     test_assert(inv != 0);
     // If `inv` were absent, the length would 0, so the above test is redundant.
     test_assert(inv_len == 10);
     // Index 0 is the first, index 2 is the third.
     // NOTE: C++ uses the `Get` terminology for vector elemetns, C use `at`.
     uint8_t third_item = flatbuffers_uint8_vec_at(inv, 2);
     test_assert(third_item == 2);
 
     ns(Weapon_vec_t) weapons = ns(Monster_weapons(monster));
     size_t weapons_len = ns(Weapon_vec_len(weapons));
     test_assert(weapons_len == 2);
     // We can use `const char *` instead of `flatbuffers_string_t`.
     const char *second_weapon_name = ns(Weapon_name(ns(Weapon_vec_at(weapons, 1))));
     int16_t second_weapon_damage =  ns(Weapon_damage(ns(Weapon_vec_at(weapons, 1))));
     test_assert(second_weapon_name != 0 && strcmp(second_weapon_name, "Axe") == 0);
     test_assert(second_weapon_damage == 5);
 
     // Access union type field.
     if (ns(Monster_equipped_type(monster)) == ns(Equipment_Weapon)) {
         // Cast to appropriate type:
         // C does not require the cast to Weapon_table_t, but C++ does.
         ns(Weapon_table_t) weapon = (ns(Weapon_table_t)) ns(Monster_equipped(monster));
         const char *weapon_name = ns(Weapon_name(weapon));
         int16_t weapon_damage = ns(Weapon_damage(weapon));
 
         test_assert(0 == strcmp(weapon_name, "Axe"));
         test_assert(weapon_damage == 5);
     }
     return 0;
 }
 
 #include <stdio.h>
 
 int main(int argc, char *argv[])
 {
     // Create a `FlatBufferBuilder`, which will be used to create our
     // monsters' FlatBuffers.
     flatcc_builder_t builder;
     void  *buf;
     size_t size;
 
     // Silence warnings.
     (void)argc;
     (void)argv;
 
     // Initialize the builder object.
     flatcc_builder_init(&builder);
     test_assert(0 == create_monster_bottom_up(&builder, 0));
 
     // Allocate and extract a readable buffer from internal builder heap.
     // NOTE: Finalizing the buffer does NOT change the builder, it
     // just creates a snapshot of the builder content.
     // NOTE2: finalize_buffer uses malloc while finalize_aligned_buffer
     // uses a portable aligned allocation method. Often the malloc
     // version is sufficient, but won't work for all schema on all
     // systems. If the buffer is written to disk or network, but not
     // accessed in memory, `finalize_buffer` is also sufficient.
     // The flatcc_builder version of free or aligned_free should be used
     // instead of `free` although free will often work on POSIX systems.
     // This ensures portability and prevents issues when linking to
     // allocation libraries other than malloc.
     buf = flatcc_builder_finalize_aligned_buffer(&builder, &size);
     //buf = flatcc_builder_finalize_buffer(&builder, &size);
 
     // We now have a FlatBuffer we can store on disk or send over a network.
     // ** file/network code goes here :) **
     // Instead, we're going to access it right away (as if we just received it).
     //access_monster_buffer(buf);
 
     // prior to v0.5.0, use `aligned_free`
     flatcc_builder_aligned_free(buf);
     //free(buf);
     //
     // The builder object can optionally be reused after a reset which
     // is faster than creating a new builder. Subsequent use might
     // entirely avoid temporary allocations until finalizing the buffer.
     flatcc_builder_reset(&builder);
     test_assert(0 == create_monster_bottom_up(&builder, 1));
     buf = flatcc_builder_finalize_aligned_buffer(&builder, &size);
     access_monster_buffer(buf);
     flatcc_builder_aligned_free(buf);
     flatcc_builder_reset(&builder);
     create_monster_top_down(&builder);
     buf = flatcc_builder_finalize_buffer(&builder, &size);
     test_assert(0 == access_monster_buffer(buf));
     flatcc_builder_free(buf);
     // Eventually the builder must be cleaned up:
     flatcc_builder_clear(&builder);
 
     printf("The FlatBuffer was successfully created and accessed!\n");
 
     return 0;
 }